Coating Having Macroscopic Texture and Process for Making Same

ABSTRACT

In one embodiment the present invention provides a coated substrate comprising a substrate, a radiation-cured coating or a thermally-cured on at least a portion of the substrate, wherein the coating comprises an inherent macroscopic texture. In another embodiment, the present invention provides a pre-cured coating mixture comprising a radiation-curable resin and an initiator, or a thermally-curable resin and thermal initiator, wherein the radiation- or thermally-curable resin and the respective initiator form a pre-cured coating mixture capable of forming a macroscopic texture upon application of the mixture on a substrate. In another embodiment the present invention provides a pre-cured coating mixture comprising a radiation- or thermally-curable resin, an initiator, and texture-producing particles having an effective size to provide a macroscopic texture upon application of the mixture on a substrate. In another embodiment, the present invention provides a coated substrate comprising a substrate and a radiation- or thermally-cured coating oil at least a portion of the substrate, wherein the coating comprises an inherent macroscopic texture. 
     In addition, the present invention provides a process for making a coating on a substrate, comprising the steps of distributing a pre-cured coating mixture comprising a radiation-curable resin and an initiator or a thermally-curable resin and thermal initiator over at least a portion of a substrate to form a pre-cured coating having a macroscopic texture, and radiation-curing or thermally curing, respectively, the pre-cured coating to form a radiation-cured or thermally-cured coating having the macroscopic texture.

This application is a continuation-in-part of U.S. application Ser. No.09/489,420 filed Jan. 21, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to a coating composition and process formaking and applying the coating. More specifically, the inventionrelates to radiation-cured and thermally-cured coatings having amacroscopic texture that provides superior abrasion resistance andunique aesthetic qualities.

2. Description of Related Art

Radiation-curable coatings are used in many applications throughout thecoatings industry, such as protective coatings for various substrates,including plastic, metal, wood, ceramic, and others, and the advantagesof radiation-curing compared to thermal curing are well known in theart. These coatings are typically resin-based mixtures that are usuallycured using ultraviolet (UV) radiation. The resins are typicallymixtures of oligomers and monomers that polymerize upon exposure to UVradiation resulting in a cured coating.

Various other components may be added to the resin mixture. Aphotosensitizer or photoinitiator may be added to cause cross-linkage ofthe polymers upon exposure to UV radiation. Flatting agents, such assilica, may be added to reduce or control the level of gloss in thecured coating; however, U.S. Pat. No. 4,358,476 discloses that excessiveconcentrations of flatting agents may result in undesirably highviscosities impeding proper application of the coating to a substrate,potential separation of the resin into separate phases, and adeleterious effect on the efficacy of the UV radiation. U.S. Pat. No.5,585,415 describes the use of a pigmented composition and variousphotoinitiators that produce a uniform microscopic surface wrinklingthat provides a low gloss surface without the use of flatting agents.Various other components, such as fillers, plasticizers, antioxidants,optical brighteners, defoamers, stabilizers, wetting agents, mildewcidesand fungicides, surfactants, adhesion promoters, colorants, dyes,pigments, slip agents, fire and flame retardants, and release agents,may also be added to the resin mixture to provide additionalfunctionality.

An important aspect of these coatings is their level of scratch orabrasion resistance. Good abrasion resistance is desirable so that theintegrity and appearance of the coating is maintained. For example, asuperior abrasion-resistant coating would be desirable for a flooringsubstrate, since flooring is typically exposed to a variety ofabrasives. Improvements in the abrasion-resistance of coatings has beenaccomplished through various techniques. U.S. Pat. No. 4,478,876describes the addition of colloidal silica to hydrolyzable silanes andpolymers derived from a combination of acryloxy functional silanes andpolyfunctional acrylate monomers. Another technique is the use ofcompositions containing acrylate or methacrylate functionalities on amonomer, oligomer, or resin. U.S. Pat. No. 5,104,929 describes the useof colloidal silica dispersions in certain acrylate or methacrylateester monomers or mixtures thereof U.S. Pat. No. 5,316,855 describes theuse of a cohydrolyzed metal alkoxide sol with atrialkoxysilane-containing organic component having the trialkoxysilane.

These radiation-cured coatings generally have a substantially smooth,exposed surface such that there is no macroscopic texture or texturevisible to the naked eye. This type of smooth surface provides for easeof cleaning. Some radiation-cured coatings have a microscopic texture asdescribed in U.S. Pat. No. 5,585,415. The individual features of thistexture are not visible to the naked eye, but the combined effect of themicroscopic texture results in the scattering of visible light, thatresults in a matte or low gloss appearance. This texture is provided bythe coating curing process which results in microscopic wrinkles on thesurface of the coating. While the microscopic dimensions of this textureprovide a matte finish, these dimensions also make the coatingsusceptible to particle entrapment within the microscopic wrinkles. Thisparticle entrapment results in a visibly dirty surface that is difficultto clean. Another microscopic texture found in radiation-curablecoatings results from the addition of flatting agents to the uncuredcoating mixture. During the curing process these flatting agents, whichare small inorganic or organic particles, concentrate at the coatingsurface to form a microscopically rough surface that scatters visiblelight resulting in a matte finish. The size of the particle used istypically such that it is no larger in diameter than the averagethickness of the cured coating. Particles much larger than the coatingthickness do not result in a matte finish and are not desired. Sincemost radiation-cured coatings are no more than 75-100 μm thick, andsince UV radiation can not typically penetrate any deeper, typicalflatting agent particles for UV-cured coatings range in size from0.1-100 μm, depending upon average coating thickness. Flatting agentsare well known in the art as described, for example, in F. D. C.Gallouedec et al., “Optimization of Ultrafine Microporous Powders toObtain Low-Gloss UV Curable Coatings,” Radtech Report, September/October1995, pp 18-24.

To produce such macroscopically smooth surfaces requires the applicationof a coating mixture that can be easily distributed across the substrateto be coated. if the coating mixture has a high viscosity, for example,the coating will not distribute smoothly. Therefore, it is preferable touse a lower viscosity coating to produce such a macroscopically smoothcoating surface.

Thermally-cured coatings are also used in many applications throughoutthe coatings industry for various substrates such as plastic, metal,wood, ceramic, and others. Thermally-cured coatings are similar toradiation-cured coatings in that they typically comprise resin-basedmixtures of oligomers and monomers that polymerize upon curing. Insteadof using radiation to cure or polymerize the resin, however, heat isused to affect polymerization. As such, a thermally-activated initiatoris used to initiate polymerization, rather than a photosensitizer orphotoinitiator. However, various other components may be added to thethermally-curable resin mixture, including the same components that areadded to radiation-curable resin mixture, such as flatting agents,fillers, plasticizers, antioxidants, optical brighteners, defoamers,stabilizers, wetting agents, mildewcides and fungicides, surfactants,adhesion promoters, colorants, dyes, pigments, slip agents, fire andflame retardants, and release agents.

Similar to the radiation-cured coatings, however, thermally-curedcoatings are also substantially smooth from a macroscopic perspective.Also, to produce such macroscopically smooth surfaces requires theapplication of a coating mixture that can be easily distributed acrossthe substrate to be coated. If the coating mixture has a high viscosity,for example, the coating will not distribute smoothly. Therefore, aswith radiation-cured coatings, it is preferable to use a lower viscositycoating to produce such a macroscopically smooth coating surface.

Other coatings provide a macroscopically textured surface but by methodsother than radiation-curing or thermal-curing. In chemical embossing,for example, a macroscopic texture is formed based upon the use ofvarious chemicals added to the substrate. In mechanical embossing, thesubstrate itself is imprinted with the desired textural pattern. In bothtypes of embossing, the subsequently applied coating naturally conformsto the shape of the substrate textural pattern. However, any desiredchange to the textural pattern requires changes in the amount and typeof chemicals added to the substrate and/or the replacement of the rollerused to mechanically imprint the pattern on the substrate, which can besignificantly expensive and time consuming. Furthermore, neither thecoating itself or its application are inherently providing the desired.texture. In another form of mechanical embossing, texture may beachieved by impressing a given pattern on the cured coating itself.Similarly, however, the texture is not produced inherently by thecoating itself or its application.

Based on the foregoing, there is a need for a superiorabrasion-resistant, radiation-cured and thermally-cured coatings forvarious substrates including plastic, metal, wood, and ceramic, amongothers, having a macroscopic texture. In addition. there is a need for acoating having a macroscopic texture that is easily cleanable and thatprovides certain aesthetic properties. Further, there is a need for amethod to produce such a superior abrasion-resistant, radiation-curedcoating having a macroscopic texture using a high viscosity pre-curedcoating mixture and/or texture-producing particles.

SUMMARY OF THE INVENTION

In one embodiment the present invention provides a coated substratecomprising a substrate, a radiation-cured coating on at least a portionof the substrate, wherein the coating comprises an inherent macroscopictexture. In another embodiment, the present invention provides apre-cured coating mixture comprising a radiation-curable resin and aninitiator, wherein the radiation-curable resin and the initiator form apre-cured coating mixture capable of formming a macroscopic texture uponapplication of the mixture on a substrate. In another embodiment thepresent invention provides a pre-cured coating mixture comprising aradiation-curable resin, an initiator, and texture-producing particleshaving an effective size to provide a macroscopic texture uponapplication of the mixture on a substrate.

In yet another embodiment, the present invention provides a coatedsubstrate comprising a substrate, a thermally-cured coating on at leasta portion of the substrate, wherein the coating comprises an inherentmacroscopic texture. In another embodiment, the present inventionprovides a pre-cured coating mixture comprising a thermally-curableresin and a thermal initiator, wherein the thermally-curable resin andthe thermal initiator form a pre-cured coating mixture capable offorming a macroscopic texture upon application of the mixture on asubstrate. In another embodiment the present invention provides apre-cured coating mixture comprising a thermally-curable resin, athermal initiator, and texture-producing particles having an effectivesize to provide a macroscopic texture upon application of the mixture ona substrate.

In addition, the present invention provides a process for making acoating on a substrate, comprising the steps of distributing a pre-curedcoating mixture comprising a radiation-curable resin and an initiator ora thermally-curable resin and thermal initiator over at least a portionof a substrate to form a pre-cured coating having a macroscopic texture,and radiation-curing or thermally curing, respectively, the pre-curedcoating to form a radiation-cured or thermally-cured coating having themacroscopic texture.

The coating of the present invention provides a top coat or protectivecoating having a macroscopic texture to substrates containing plasticsuch as polyvinyl chloride, metal, cellulose, fiberglass, wood, andceramic, among others. In a preferred embodiment the coating of thepresent invention is used in connection with sheet flooring. In anadditionally preferred embodiment, the coating of the present inventionis used in connection with floor tiles. The coating of the presentinvention provides superior scratch or abrasion resistance and goodtransparency. In addition, the coating of the present invention iseasily cleanable, and the macroscopic texture provides an aestheticaspect to the coating.

Other embodiments and features of the present invention will appear fromthe following description in which the preferred embodiments are setforth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a coated substrate 10 accordingto one embodiment of the present invention;

FIG. 2 illustrates a cross-sectional view of a coated substrateaccording to another embodiment of the present invention;

FIG. 3 illustrates a cross-sectional view of a coated substrateaccording to yet another embodiment of the present invention;

FIG. 4 is a process flow diagram of a process for making a coatingaccording to one embodiment of the present invention;

FIG. 4B illustrates a cross-sectional. view of a coated substrateaccording to yet another embodiment of the present invention;

FIG. 4C is a cross-sectional view of a vinyl tile according to oneembodiment of the present invention;

FIG. 4D is a process flow diagram of a process for applying a coating ofthe present invention to a tile substrate according to one embodiment ofthe present invention;

FIG. 4E illustrates a cross-sectional view of a coated substrateaccording to yet another embodiment of the present invention;

FIG. 5 is a graph of the viscosity as a function of the shear rate for apre-cured coating mixture made according to one embodiment of thepresent invention;

FIG. 6 is a graph of the viscosity as a function of the shear rate for apre-cured coating mixture made, according to another embodiment of thepresent invention;

FIG. 7 is a graph of the viscosity as a function of time for a pre-curedcoating mixture made according to one embodiment of the presentinvention;

FIG. 8 is a graph of the viscosity as a function of the silaneconcentration in a pre-cured coating mixture made according to oneembodiment of the present invention;

FIG. 9 is a photograph of the top of a portion of the coated substrateproduced according to one embodiment of the present invention;

FIG. 10 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 11 is an illustration of the coated texture of FIG. 9;

FIG. 12 is an illustration of the coated texture of FIG. 10;

FIG. 13 is an illustration of the general type of macroscopic textureaccording to one embodiment of the present invention;

FIG. 14 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 15 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 16 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 17 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 18 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 19 is an illustration of the coated texture of FIG. 14;

FIG. 20 is an illustration of the coated texture of FIG. 15;

FIG. 21 is an illustration of the coated texture of FIG. 16;

FIG. 22 is an illustration of the coated texture of FIG. 17;

FIG. 23 is an illustration of the coated texture of FIG. 18;

FIG. 24 is an illustration of the general type of macroscopic textureaccording to another embodiment of the present invention;

FIG. 25 is an enlarged view of a portion of FIG. 24;

FIG. 26 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 27 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 28 is a photograph of the top of a portion of the coated substrateproduced according to another embodiment of the present invention;

FIG. 29 is an illustration of the coated texture of FIG. 26;

FIG. 30 is an illustration of the coated texture of FIG. 27;

FIG. 31 is an illustration of the coated texture of FIG. 28;

FIG. 32 is an illustration of the general type of macroscopic textureaccording to another embodiment of the present invention; and

FIG. 33 is a graph of the results of scratch resistance tests forseveral coatings made according to various embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a coating having a macroscopic texturethat exhibits superior abrasion-resistance, aesthetic value, and ease ofcleaning. It should be appreciated that an important aspect of thepresent invention is that the macroscopic texture is provided inherentlyby the coating itself. In addition, the present invention provides apre-cured coating mixture and a process for using the pre-cured coatingmixture to generate the coating of the present invention on a substrate.

It should be appreciated that the term “coating” refers to the curedcoating that typically would reside as an outer or exposed layer on asubstrate after it has been cured or finally processed. The terms“radiation-cured” and “thermally-cured” mean after curing has occurred;therefore, the coating of the present invention, for example, may alsobe referred to as a “radiation-cured coating” or a “thermally-curedcoating.” The terms “radiation-curable” and “thermally-curable” meanprior to curing or capable of being cured, and the term “pre-cured”means prior to curing.

In one embodiment of the present invention, the pre-cured coatingmixture generally comprises a radiation-curable resin and an initiator.The radiation-curable resin may be any resin capable of being curedusing radiant energy. Radiant energy can be transferred through wavephenomenon and subatomic particle movement. Most preferred forms ofradiant energy are ultraviolet (UV) and electron beam energy.Preferably, the radiation-curable resin comprises organic monomers,oligomers, or both. U.S. Pat. Nos. 4,169,167, 4,358,476, 4,522,958,5,104,929, 5,585,415, 5,648,40, and 5,858,809, incorporated herein byreference, describe various resins, including crosslinkable(thermosetting) resins, that may be used in the present invention.

More preferably, the radiation-curable, resin comprises a mixture ofcrosslinkable monomers and oligomers that contain on average from 1-20reactive groups per molecule of monomer or oligomer, where the reactivegroup provides the functionality for polymerization upon exposure toradiation. More preferably, the number of reactive groups per molecularis from 1-6. Preferred reactive groups include acrylate, vinyl, lactone,oxirane, vinyl ether, and hydroxyl. More preferred reactive groupsinclude acrylate, oxirane, vinyl ether, and hydroxyl. The most preferredmonomers and oligomers, however, are acrylates. Acrylates have thefollowing structure:

CH₂═CR—CO—

where R can be hydrogen, or alkyl including, but not limited to methyl,ethyl, propyl, butyl, etc. These radiation-curable resins are readilyavailable or may be synthesized by procedures well known to one of skillin the art. It is noted that the term “radiation-cured groups” refers tothese reactive groups after they have been cured.

The oligomers and monomers can also have 1-100 non-radiation-curablefunctional groups per molecule of monomer or oligomer. Preferrednon-radiation-curable functional groups include urethane, melamine,triazine, ester, amide, ethylene oxide, propylene oxide, and siloxane.More preferred non-reactive groups are urethane ester, ethylene oxide,and propylene oxide.

As will be further described below in connection with the process formaking the coating of the present invention, the concentration of theradiation-curable resin is dependent upon several factors. In onepreferred embodiment, the concentration of the radiation-curable resinis selected to provide an effective or desired viscosity of thepre-cured coating mixture. The effective viscosity of the pre-curedcoating mixture is that viscosity capable of producing a macroscopictexture, described below, upon application of the pre-cured coatingmixture to a substrate and subsequent curing. Preferably, the viscosityof the pre-cured coating mixture is approximately 100,000-1,000,000 cPsat a shear rate of 0.150 s⁻¹ at the application temperature. Therefore,the radiation-cured resin may comprise approximately 50-99%, by weightof the pre-cured coating mixture to provide the desired viscosity.Preferably, the radiation-cured resin comprises approximately 70-99%, byweight, of the pre-cured coating mixture. Of course, the viscosity ofthe pre-cured coating mixture, and, therefore, the concentration of theradiation-curable resin, will be affected by the use of additionalcomponents in the pre-cured coating mixture such as rheological controlagents, which will be described below. Other factors that affect theconcentration of the radiation-curable resin are well known to one ofskill in the art.

The initiator may be any chemical capable of assisting or catalyzing thepolymerization and crosslinking of the radiation-curable resin uponexposure to radiation. The initiator may generally be a photoinitiatoror photosensitizer. Such initiators are well known in the art and may beselected based upon the curing conditions used (e.g., curing in an inertenvironment or in air). Specifically, the initiator may be a freeradical photoinitiator, a cationic photoinitiator, and mixtures of bothof these. Preferred free radical photoinitiators include acyl phosphineoxide derivatives, benzophenone derivatives, and mixtures thereof.Preferred cationic photoinitiators include triarylsulphonium salts,diaryliodonium salts, ferrocenium salts, and mixtures thereof. It shouldbe appreciated that the initiator refers to the initiator both beforeand after curing. Therefore, the initiator may have a different chemicalstructure or composition in the radiation-cured coating after exposureto radiation.

The concentration of a particular initiator is that amount necessary toprovide satisfactory curing for a given proved resin based upon theproperties of that particular initiator. Such concentrations can bereadily identified by one of skill in the art. A preferred concentrationof the initiator is 0.01-10 parts per hundred resin (phr), and a morepreferred concentration is 0.1-4 phr.

The pre-cured coating mixture may also comprise a rheological controlagent (RCA), particularly if the pre-cured coating mixture does not havean inherent viscosity that is high enough to form a macroscopic textureupon application of the pre-cured coating mixture to a substrate. TheRCA may be inorganic particles, organic solids, and mixtures of both.

The inorganic particles may be any inorganic solid having a size that issmall enough to be included in the pre-cured coating mixture withoutdeleteriously affecting the pre-cured coating mixture's ability to cureand adhere to a substrate. The particle should also be sufficientlysmall and/or closely match the refractive index of the cured coatingsuch that the opacity of the cured coating is minimized. The particleshould also not deleteriously affect the cured coating's abrasionresistance and in some cases it can improve that property. Additionally,the particle should not deleteriously affect the resistance of the curedcoating to chemical attack by strongly basic aqueous media (i.e., thealkali resistance of the coating), since such alkali resistance isimportant in flooring materials. It should be appreciated that the sizeof these particles is such that they do not directly provide orcontribute to the macroscopic texture. Preferred sizes of the inorganicparticles are 1-100 nm, where 10-60 nm are most preferred.

Preferably, the inorganic particles are metal oxides, metals, orcarbonates, where metal oxides are preferred. More preferably, theinorganic particles are alumina, aluminosilicates, alumina coated onsilica, silica, fumed alumina, fumed silica, calcium carbonate, andclays. Still more preferred is alumina due to its superior hardness (forabrasion resistance) and for its greater alkali resistance relative tosilica. Most preferred is nanometer-sized alumina with a particle sizerange of 27-56 nm due to the enhanced cured coating transparencyafforded by such small particles when they are well-dispersed (e.g.,through the use of an appropriate amount and type of coupling agent).However, since alumina has a higher refractive index (i.e., ˜1.7) thanmost organic coatings and silica (both ˜1.5), it may be envisioned thata nanometer-sized aluminosilicate material will give the optimalcombination of transparency, abrasion resistance, and alkali resistance.

The inorganic particles may comprise approximately 1-80%, by weight, ofthe pre-cured coating mixture, more preferably 1-50%, by weight, andmost preferably 1-25%, by weight. Even more preferably, ifnanometer-sized alumina is used, its concentration is approximately1-40%, by weight, of the pry coating mixture. If fumed silica is used,its concentration is approximately 1-10%, by weight, of the pre-curedcoating mixture. If nanometer-sized chine silica is used, itsconcentration is approximately 10-30%, by weight, of the procuredcoating mixture. If exfoliated clay is used, its concentration isapproximately 10-30%, by weight, of the pre-cured coating mixture.

Similarly, the organic solids may be any organic solid having a sizethat is small enough to be included in the pre-cured coating mixturewithout deleteriously affecting the pre-cured coating mixture's abilityto cure and adhere to a substrate. As with the inorganic particles, theorganic particles should also not deleteriously affect the curedcoating's transparency or abrasion resistance. Unlike the inorganicparticles, the organic particles may dissolve or partially dissolve intothe pre-cured resin at elevated temperature and thicken the pre-curedcoating mixture upon cooling. The organic solids may be low molecularweight waxes containing functionality such as acid, amine, amide,hydroxyl, urea; polymers of ethylene glycol; polymers of propyleneglycol; natural polymers such as guar, gelatin, and corn starch;polyamides; polypropylene; and mixtures of any of these. Most preferredare functional waxes. The organic solids may comprise approximately1-50%, by weight, of the pre-cured coating mixture. More preferably, theorganic solids comprise between approximately 1-20%, by weight. Mostpreferably, if functional waxes are used, their concentration isapproximately 1-10%, by weight, of the pre-cured coating mixture. Aswill be described below in connection with the process for making thecoating of the present invention, the RCA may added for severalpurposes.

A coupling agent or dispersing agent may also be added for purpose ofaiding the dispersion of the RCA in the pre-cured coating mixture. Thecoupling agent may be any material that provides surfactant-likeproperties and is capable of enhancing the dispersion of the RCA in thepre-cured coating mixture, in particular, the dispersion of inorganicparticles. The coupling agent ideally forms a chemical and/or physicalbond with the pre-cured coating mixture and the inorganic particle,which improves the adhesion of the particle to the pre-cured coatingmixture. Generally, the coupling agent is a organo-silicon ororgano-fluorine containing molecule or polymer. Preferred organo-siliconmaterials are organosilanes and more preferably a prehydrolyzedorganosilane. The coupling agent may also be vinyl phosphonic acid ormixtures of phosphonic acid with the prehydrolyzed organosilane. Theconcentration of the dispersing agent may be approximately 0.1-20%, byweight in the pre-cured coating mixture, and more preferablyapproximately 0.1-15%, by weight.

A flatting agent may also be added to the procured coating mixture ofthe present invention. Flatting agents are well known in the art.Preferred flatting agents include organic particles having a size ofapproximately 0.1-100 microns, inorganic particles having a size ofapproximately 0.1-100 microns, and mixes of both. When flatting agentsart used, a coupling agent may be needed to obtain good dispersion inthe pre-cured coating mixture and good adhesion between the particle andthe cured coating. For inorganic flatting agents, preferred couplingagents are organosilanes, mixtures of organosilanes, and low surfacetension monomers and oligomers. For organic flatting agents, preferredcoupling agent include organosilanes, mixtures of organosilanes, and lowsurface tension monomers and oligomers. The particle size selected issuch that it is about the same size as the coating thickness or smaller.More preferred flatting agents include silica, alumina, polypropylene,polyethylene, waxes, ethylene copolymers, polyamide,polytetrafluoroethylene, urea-formaldehyde and combinations thereof. Theconcentration of the flatting agent may be approximately 2-25%, byweight, of the pre-cured coating mixtures and more preferably is 5-20%,by weight.

In addition to the foregoing components of the pre-cured coatingmixture, texture-producing particles may also be added. Suchtexture-producing particles have an effective size or an averagediameter that is larger than the pre-cured coating thickness after ithas been applied to a substrate. These texture-producing particles,therefore, may act to provide the macroscopic texture of the coating ofthe present invention. It should be appreciated that thesetexture-producing particles may be added to a pre-cured coating mixturethat has an effective viscosity for macroscopic texture or to apre-cured coating mixture that does not have an effective viscosity formacroscopic texture. In the latter case, the macroscopic texture wouldbe produced only by the texture-producing particles.

The degree of texture provided by the texture-producing particles iscontrolled by the ratio of the particle size to the thickness of thecured coating. As this ratio increases from 1, the texture becomesmacroscopic and can be made more aggressive, (visibly more rough) as theratio is increased. The degree of aggressiveness of the texture isdetermined by the desired end use properties such as abrasion resistanceand cleanability. It is important that the particles selected have goodadhesion to the cured coating. These particles can be inorganic ororganic materials. A coupling agent may be necessary to obtain gooddispersion in the pre-cured coating mixture and good adhesion betweenthe particle and the cured coating. Preferred inorganic particles areglass, ceramic, alumina, silica, aluminosilicates, and alumina coated onsilica. Preferred coupling agents for inorganic texture-producingparticles are organosilanes. Preferred organic particles arethermoplastic and thermosetting polymers. For inorganic flatting agents,preferred coupling agents are organosilanes, mixtures of organosilanes,and low surface tension monomers and oligomers. For organic flattingagents, preferred coupling agents include organosilanes, mixtures oforganosilanes, and low surface tension monomers and oligomers. Mostpreferred organic particles are polyamide, including nylons,specifically, nylon 6 and nylon 12 (although one of skill in the artwill recognize that other nylons may be used in the present invention),polypropylene, polyethylene, polytetrafluoroethylene, ethylenecopolymers, waxes, epoxy, and urea-formaldehyde. Preferred averageparticle size of both organic and inorganic particles is 30-350 μm. Mostpreferred is 30-150 μm. Preferred concentration of particles in thepre-cured coating mixture is 1-30%, by weight. The most preferredconcentration is 5-15% by weight.

A preferred embodiment of a pre-cured coating mixture of the presentinvention comprises, by weight, 79.44% of a resin mixture comprising, byweight, 53.40%, urethane acrylate (Alua 1001, available from CongoleumCorporation, Mercerville, N.J.), 8.8% ethoxylated diacrylate (SR 259available from Sartomer, Exton, Pa.), 24.3% propoxylated diacrylate (SR306 available from Sartomer, Exton, Pa.), 13.4% ethoxylatedtrimethlyolpropane triacrylate (SR 454 available from Sartomer, Exton,Pa.), and 0.1% acylphosphine oxide (Luceirin TPO available from BASF,Charlotte N.C.), 12.00% flatting agent comprising 5 micron nylonparticles (Orgasol 2001 UD available from Atofina, Philadelphia, Pa.);6.25% texture-producing particles comprising 60 micron nylon 12particles (Orgasol 2002 ES 6 available from Atofina, Philadelphia, Pa.);2.00% alumina RCA having a particle size distribution in the range of27-56 nm (Nanotek Alumina #0100 available from Nanophase TechnologiesCorp. Burr Ridge, Ill.); and 0.31% prehydrolyzed silane as an RCAcoupling agent comprising 0.21% 3-methacryloxypropyltrimethoxysilane(Z-6030 available from Dow Corning, Midland, Mich.), 0.015% glacialacetic acid, 0.015% deionized water, and 0.07% ethanol, prehydrolyzed asdescribed in Example 1 below. As such, a preferred cured coatingaccording to the present invention is that coating produced using theabove preferred pre-cured coating mixture. In particular, this pre-curedcoating mixture and the resulting cured coating are preferred for use onsheet flooring as a substrate.

An even more preferred embodiment of a pre-cured coating mixture of thepresent invention comprises, by weight, 84.59% of a resin mixturecomprising, by weight, 53.4% urethane acrylate (Alua 1001, availablefrom Congoleum Corporation, Mercerville, N.J.), 8.8% ethoxylateddiacrylate (SR 259 available from Sartomer, Exton, Pa.), 24.3%.propoxylated diacrylate (SR 306 available from Sartomer, Exton, Pa.),13.3% ethoxylated trimethlyolpropane triacrylate (SR 454 available fromSartomer, Exton, Pa.), and 0.2% acylphosphine oxide (Luceirin TPOavailable from BASF, Charlotte, N.C.); 8.0% flatting agent comprising 5micron nylon particles (Orgasol 2001 UD available from Atofina,Philadelphia, Pa.); 6.25% texture-producing particles comprising 60micron nylon 12 particles (Orgasol 2002 ES 6 available from Atofina,Philadelphia, Pa.); 1.0% alumina RCA having a particle size distributionin the range of 27-56 nm (Nanotek Alumina #0100 available from NanophaseTechnologies Corp. Burr Ridge, Ill.); and 0.16% prehydrolyzed silane asan RCA coupling agent composing 0.21%3-methacryloxypropyltrimethoxysilane (Z-6030 available from Dow Corning,Midland, Mich.), 0.015% glacial acetic acid, 0.015% deionized water, and0.07% ethanol prehydrolyzed as described in Example 1 below. As such, apreferred cured coating according to the present invention is thatcoating produced using the above preferred pre-cured coating mixture. Inparticular, this pre-cured coating mixture and the resulting curedcoating are preferred for use on sheet flooring as a substrate.

In another preferred embodiment, a pre-cured coating mixture for usewith tile as the substrate comprises, by weight, 35.303% ethoxylatedtrimethylolpropane triacrylate (SR 454, available from Sartomer, Exton,Pa.), 41.050% polyester acrylate (Laromer PE56F, available from BASF,Charlotte, N.C.), 5.747% urethane acrylate (Alua 1001, available fromCongoleum Corporation, Mercerville, N.J.), 0.330% acylphosphine oxide(Luceirin TPO, available from BASF, Charlotte, N.C.), 8.000% 3 microninorganic flatting agent (Acematte OK 412, available from Degussa Corp.,Ridgefield Park, N.J.), 2.323% prehydrolyzed silane as an RCA couplingagent comprising 0.21% 3-methacryloxypropyltrimethoxysilane (Z-6030available from Dow Corning, Midland, Mich.), 0.015% glacial acetic acid,0.015% deionized water, and 0.07% ethanol, prehydrolyzed as described inExample 1 below, 1.000% inorganic RCA (Nanotek Alumina #0100, availablefrom Nanophase Technologies, Burr Ridge, Ill.), and 6.250% 60 microntexture-producing particle (Orgasol 2002 ES6, available from Atofina,Philadelphia, Pa.). As such, a preferred cured coating according to thepresent invention is that coating produced using the above preferredpre-cured coating mixture.

In another embodiment of the present invention, the pre-cured coatingmixture comprises a thermally-curable resin and a thermal initiator. Thethermally-curable resin may be any resin capable of being cured usingthermal energy. The thermally-curable resins preferably include organicmonomers, oligomers, or both. U.S. Pat. Nos. 4,169,167, 4,358,476,4,522,958, 5,104,929, 5,585,415, 5,648,40, and 5,858,809, incorporatedherein by reference, describe various resins, including crosslinkable(thermosetting) resins, that may be used in the present invention. Thethermal initiator used for thermally-curable coatings of the presentinvention is any thermal initiator known in the art. Preferably, thefree radical thermal initiator is an organic peroxide, such astertiary-butyl peroxybenzoate.

More preferably, the thermally-curable resin comprises a mixture ofcrosslinkable monomers and oligomers that contain on average from 1-20reactive groups per molecule of monomer or oligomer, where the reactivegroup provides the functionality for polymerization upon exposure toheat. More preferably, the number of reactive groups per molecular isfrom 1-6. Preferred reactive groups include acrylate, vinyl, lactone,oxirane, vinyl ether, and hydroxyl. More preferred reactive groupsinclude acrylate, oxirane, vinyl ether, and hydroxyl. The most preferredmonomers and oligomers, however, are acrylates. Acrylates have thefollowing structure:

CH₂═CR—CO—

where R can be hydrogen, or alkyl, including, but not limited to,methyl, ethyl, propyl, butyl, etc. These thermally-curable resins arereadily available or may be synthesized by procedures well known to oneof skill in the art. It is noted that the term “thermally-cured groups”refers to these reactive groups after they have been cured.

The oligomers and monomers can also have 1-100 non-thermally-curablefunctional groups per molecule of ester, amide, ethylene oxide,propylene oxide, and siloxane. More preferred non-reactive groups areurethane, ethylene oxide, and propylene oxide.

As will be further described below in connection with the process formaking the coating of the present invention, the concentration of thethermally-curable resin is dependent upon several factors. In onepreferred embodiment, the concentration of the thermally-curable resinis selected to provide an effective or desired viscosity of thepre-cured coating mixture. The effective viscosity of the pre-curedcoating mixture is that viscosity capable of producing a macroscopictexture, described below, upon application of the pre-cured coatingmixture to a substrate and subsequent curing. Preferably, the viscosityof the pre-cured coating mixture is approximately 100,000-1,000,000 cPsat a shear rate of 0.150 s⁻¹ at the application temperature. Therefore,the thermally-cured resin may comprise approximately 50-99%, by weightof the pre-cured coating mixture to provide the desired viscosity.Preferably, the thermally-cured resin comprises approximately 70-99%, byweight, of the pre-cured coating mixture. Of course, the viscosity ofthe pre-cured coating mixture, and, therefore, the concentration of thethermally-curable resin, will be affected by the use of additionalcomponents in the pre-cured coating mixture such as rheological controlagents, which will be described below. Other factors that affect theconcentration of the thermally-curable resin are well known to one ofskill in the art.

As with the radiation-curable coatings of the present invention, thethermally-cured coatings of the present invention also provide amacroscopic texture. A such, the same rheological control agents,coupling agents, flatting agents, and texture-producing particlespreviously described may be used with the thermally-curable coatings ofthe present invention. The manner of use of these agents with thethermally-curable coatings of the present invention is the same aspreviously described for the radiation-curable coatings.

A preferred embodiment of a thermally pre-cured coating mixture of thepresent invention comprises, by weight, 44.83% urethane acrylate (Alua1001, available from Congoleum Corporation, Mercerville, N.J.), 6.92%ethoxylated diacrylate (SR 259 available from Sartomer, Exton, Pa.),20.53% propoxylated diacrylate (SR 306 available from Sartomer, Exton,Pa.), 11.25% ethoxylated trimethylolpropane triacrylate (SR 454available from Sartomer, Exton, Pa.), 1.06% tertiary-butylperoxybenzoate (P-20 available from Norac, Azusa, Calif.) 8% flattingagent comprising 5 micron nylon 12 particles (Orgasol 2001 UD availablefrom Atofina, Philadelphia, Pa.), 6.25% texture-producing particlescomprising 60 micron nylon 12 particles (Orgasol 2002 ES6 available fromAtofina, Philadelphia, Pa.), 1% alumina RCA having a particle sizedistribution in the range of 27-56 nm, and nominally 35 nm, (NanotekAlumina #0100 available from Nanophase Technologies Corp. Burr Ridge,Ill.), and 0.16% prehydrolyzed silane as an RCA coupling agentcomprising 0.21% 3-methacryloxypropyltrimethoxysilane (Z-6030 availablefrom Dow Corning, Midland, Mich.), 0.015% glacial acetic acid, 0.015%deionized water, and 0.07% ethanol, prehydrolyzed as described inExample 1 below. As such, a preferred cured coating according to thepresent invention is that coating produced using the above preferredpre-cured coating mixture. Another preferred embodiment is the use ofthe foregoing pre-cured coating mixture and resulting cured coating withsheet flooring as the substrate.

It should be appreciated that many additional components known in theart may be added to the coatings of the present invention. Theseadditional components may include fillers, plasticizers, antioxidants,optical brighteners, defoamers, stabilizers, wetting agents, mildewcidesand fungicides, surfactants, adhesion promoters, colorants, dyes,pigments, slip agents, fire and flame retardants, and release agents.

FIG. 1 illustrates a perspective view of a coated substrate 10 accordingto one embodiment of the present invention. In FIG. 1 a coating 12 isadhered to a substrate 14, where the coating 12 is produced by curingthe pressured coating mixture made according to the present inventioneither being a radiation-curable coating mixture or a thermally-curablecoating mixture. It should be appreciated that the coating of thepresent invention may be used in conjunction with any substrate that iscapable of remaining attached to the coating after curing. Substratesthat may be used include those containing plastic such as polyvinylchloride, metal, cellulose, fiberglass, wood, and ceramic, among others.Preferably, the substrate is a flooring material, such as a floor tileor flexible sheet, where the surface of the coating having themacroscopic texture is the exposed surface of the flooring or thatsurface upon which one would walk. The superior scratch resistance ofthe coating of the present invention, and the ease of cleaning, make thecoating particularly suitable for flooring applications.

As noted, the coating of the present invention has an inherentmacroscopic texture. The term “macroscopic texure” is intended toencompass any textural features, regular or irregular, produced on thesurface of a coating that are visible to the naked eye at close range,as opposed to microscopic texture that would require the use of amicroscope to view the texture. The macroscopic texture of the presentinvention may also provide a non-smooth surface such that the texture isapparent to the touch. Additionally, the macroscopic texture whenproduced by the use of texture-producing particles may be visible to thenaked or unaided eye at a close range. The macroscopic texture may haveany design, shape, or pattern on the surface of the coating. Thismacroscopic texture (not shown in FIG. 1) is provided by the coating 12and is visible to the naked eye when viewing the coating 12 on thecoated substrate 10.

As described above in connection with the pre-cured coating mixture, themacroscopic texture may be provided by different components in thepre-cured coating mixture. In one embodiment of the invention, themacroscopic texture is provided by a pre-cured coating mixture having aneffective viscosity capable of providing a macroscopic texture. Inanother embodiment, the macroscopic texture is provided by a pre-curedcoating mixture that comprises texture-producing particles having aneffective size to produce a cured coating with the macroscopic texture.In yet another embodiment, the macroscopic, texture may be provided by apre-cured coating mixture having both an effective viscosity andtexture-producing particles. Several examples of various coatings madeaccording, to various embodiments of the present invention are describedbelow, which provide examples of the various macroscopic textures. Theseexamples are intended to provide examples of how a macroscopic texturemay be achieved, but are not intended to be limiting as to the types,shapes, or patterns of macroscopic texture that may be obtained.

In addition, it was surprisingly found that the coatings of the presentinvention with macroscopic texture have superior scratch and abrasionresistance as measured by a Taber scratch test and traffic were panels.Scratch test results for various coatings made according to the presentinvention are described in the examples below.

It should be appreciated that the concentrations of the variousnon-reactive groups and components in the cured coating are assumed tobe the same in the pre-cured coating mixture. As will be describedbelow, the coating of the present invention is made by applying thepre-cured coating mixture to a substrate followed by eitherradiation-curing or thermal curing. Therefore, it is assumed that theconcentrations of the various non-reactive groups and components in thepre-cured coating mixture will not change substantially during curingand will remain substantially the same. However, those skilled in theart will recognize that other factors, such as coating applicationprocessing conditions, may induce some degree of variability in theseconcentrations.

FIG. 2 illustrates a cross-sectional view of a coated substrateaccording to another embodiment of the present invention. FIG. 2 shows acoated substrate 20 having a coating 22 on a coated substrate layer 24and additional substrate layers 26 attached to the coated substratelayer 22 on the side opposite the coating 22. The coating 22 illustratesthe macroscopic texture provided by the coating 22. As shown in FIG. 2,it should be appreciated that the macroscopic texture of the coatingsmade according to the present invention is inherent in, or provided by,the coating itself and is independent of the substrate to which thecoating is adhered. Therefore, it should be appreciated that thiscoating is significantly different from coatings that naturally conformto a substrate having a texture or for cured coatings that are impressedwith a pattern.

FIG. 3 illustrates a cross-sectional view of a coated substrateaccording to yet another embodiment of the present invention. FIG. 3shows a coated substrate 30 having a coating 32 on a coated substratelayer 34 and additional substrate layers 36 attached to the coatedsubstrate layer 32 on the side opposite the coating 32. FIG. 3illustrates that the coatings of the present invention may also beapplied to substrates that already have macroscopic texture themselvesdue to embossing or some other method. Thus, two or more textures canexist on a given coated substrate, i.e., texture from the coating andtexture from the substrate. As illustrated in FIG. 3, the macroscopictexture of the coating 32 may be such that it conforms to the texture ofthe underlying substrate 34. Alternatively, the macroscopic texture maybe applied so that it does not conform to the texture of the underlyingsubstrate.

FIG. 4 is a process flow diagram of a process for making a coatingaccording to one embodiment of the present invention. In the step 40,the initiator is dissolved in the radiation-curable resin. The initiatorand the resin may be mixed in any manner typically used in the art suchthat the initiator is dissolved into the resin phase.

In the step 42, any RCA, coupling agent, flatting agent, ortexture-producing particles are added to the mixture produced in thestep 40. It should be appreciated that for the RCA, flatting agent,and/or texture-producing particles, a coupling agent may also be used.In this case, the particles and the coupling agent may simply be addedto the mixture either simultaneously or sequentially, without the needto pre-treat the particles with the coupling agent before adding thesecomponents to the mixture. This avoids the use of a solvent that maycreate diffusion pathways for staining materials to diffuse through andstain the coating. In some cases, it is desirable to make a concentratedmixture of RCA, coupling agent, flatting agent, and/or texture-producingparticles in a liquid medium and dilute it down into the pre-curedcoating mixture. This concentrate is called a master batch and is wellknown in the art.

In the step 44, all of the components are mixed to produce the pre-curedcoating mixture. The step 44 may be accomplished using a Cowles blademixer, ultrasonic probe, or other high shear mixer. It should beappreciated that during mixing the temperature of the mixture should notbe allowed to increase significantly. For example, increases intemperature to approximately 100° C. may result in thermal reaction ofthe resin causing gelation. In cases where an organic solid is used as aRCA, the temperature during mixing should be allowed to increase to atemperature that is adequate to dissolve the organic solid, for example,70° C. The temperature should then be reduced to ambient temperature,thereby producing a highly viscous pre-cured coating mixture.

In one embodiment of the invention, the pre-cured coating mixtureproduced in the step 44 must have the necessary viscosity to produce amacroscopic texture upon application and subsequent curing of thepre-cured coating mixture on a substrate. Preferably, the viscosity ofthe pre-cured coating mixture should be approximately 100,000-1,000,000cPs at a shear rate of 0.150 s⁻¹ at the application temperature. As willbe further discussed below a viscosity that is too low does not providea macroscopic texture, and a viscosity that is too high results in poordistribution of the pre-cured coating mixture over the substratesurface.

To obtain the requisite, viscosity in the pre-cured coating mixturerequires the use of the appropriate concentration of theradiation-curable resin. It should be appreciated that theradiation-curable, resin may alone be used to provide the requisiteviscosity, but that it may be desirable to use a RCA in conjunction withthe radiation-curable resin to provide the requisite viscosity. If a RCAis used, then the requisite viscosity will be determined by using theappropriate concentration of both the radiation-curable resin and theRCA. It should be appreciated that in either case, the concentration ofthese components will be dependent upon the intrinsic properties ofeach. It should also be appreciated that the addition of othercomponents, such as coupling agents and flatting agents, may also affectthe viscosity of the pre-cured coating mixture. Therefore, these othercomponents may also need to be considered in determining the appropriateconcentrations of the radiation-curable resin and the RCA, if used.

In the step 46, the pre-cured coating mixture is distributed across thesurface of a substrate. The step 46 requires that the pre-cured coatingmixture is initially applied to the substrate surface and thendistributed across the surface. Application of the pre-cured coatingmixture to the surface of the substrate may be accomplished by any meansknown in the art for placing a high viscosity material onto a substrate.For example, the pre-cured coating mixture may be pumped to thesubstrate and placed on the substrate using a slot die. It should beappreciated that it may be necessary to heat the pre-cured coatingmixture to reduce the viscosity to allow for its placement on thesubstrate surface; however, it is important that the premed coatingmixture be allowed to cool prior to actually distributing it across thesubstrate surface, so that it has the required viscosity necessary togenerate macroscopic texture.

Distributing the pre-cured coating mixture across the substrate surfacemay be accomplished using any means known in the art; however, it isimportant that such means are capable of moving a high viscositymaterial across the surface in a manner that leaves the pre-curedcoating mixture in the form of the desired macroscopic texture that willbecome fixed upon curing. It should be appreciated that it is preferredto uniformly distribute the pre-cured coating across the substratesurface, but such uniform distribution should not be confused with acompletely smooth distribution of the pre-cured coating mixture acrossthe substrate surface. After the pre-cured coating mixture has beendistributed, the macroscopic texture should be apparent, as it is thistexture that will be fixed on the substrate after curing. Therefore, itshould be appreciated that, in addition to the use of an effectiveviscosity and/or texture-producing particles, the macroscopic texturecan be altered using different techniques for applying the pre-curedcoating mixture to a substrate.

Before discussing specific pre-cured coating application methods, itshould be noted that the pre-cured coatings in this embodiment can havea viscosity that is dependent on both the amount of shear applied to thepre-cured coating mixture, as well as the amount of time during andafter the application of the shear. This type of behavior is referred toin the art as thixotropic. Thus, the production of texture is dependenton the viscosity of the pre-cured coating under the shear of theapplication equipment.

One method for distributing the pre-cured coating mixture uniformlyacross the substrate surface in a manner that produces a desiredmacroscopic texture is by use of an air knife. The use of an air kniferequires that the pre-cured coating mixture has been properly anduniformly applied to the substrate surface to allow the air knife touniformly distribute the pre-cured coating mixture over the substratesurface. It should be appreciated that the relatively high viscosity ofthe pre-cured coating mixture at low shear rates allows the air knife toproduce a macroscopic texture and prohibits a macroscopically smoothdistribution of the pre-cured coating mixture. Thus, the pre-curedcoating in this embodiment of the present invention has a high enoughviscosity under the shear of the air knife to produce a macroscopictexture and not level into a macroscopically smooth surface. Morespecifically, the air knife actually generates a wave of pre-curedcoating mixture that flows over the substrate surface as it passes bythe air knife. This wave leaves behind a metered pre-cured coating withripples that are the macroscopic texture.

It should be appreciated that the operating parameters of the air knifecan be changed to produce varying macroscopic textures. These parametersinclude the line speed (dwell time under the air knife), air pressure,angle of attack, and the gap between the substrate and the air knife.Therefore, different macroscopic textures providing a variety ofaesthetic looks may be produced.

It can now be appreciated that one method for determining whether thepre-cured coating mixture has the appropriate viscosity is bydistributing the pre-cured coating mixture on the desired substrateusing an air knife. If the viscosity of the pre-cured coating under theshear of the air knife is too low, the coating will level and produce amacroscopically smooth surface. If the viscosity under shear is toohigh, the pre-cured coating mixture will be blown off the substrateresulting in an incompletely or uncoated substrate.

Another method for distributing the pre-cured coating mixture uniformlyacross the substrate surface in a manner that produces a desiredmacroscopic texture is by use of a roll coater. The roll coater bothapplies and coats the pre-cured coating mixture to the substrate. Thetexture is generated by the roller being in direct contact with thecoating on the substrate. As the substrate passes under the roller, theroller passes away from the substrate pulling or splitting some of thepre-cured coating from the substrate. This splitting results inmacroscopic texture that can be varied with the roll coater operatingparameters including line speed, gap between the roller and thesubstrate, roller material type (roller covering), engraving pattern onthe roller, roller speed relative to the line speed and roller diameter.

In the step 48 the pre-cured coating mixture that has been distributedover the substrate surface and is in the form of the desired macroscopictexture is cured using radiation. This curing step acts to polymerizethe pre-cured coating mixture to fix the macroscopic texture in placeand adhere it to the substrate surface, thereby producing aradiation-cured coating on the substrate. The step 48 may be conductedunder conditions typical of radiation-curing processes depending uponthe particular radiation-curable resin and initiator used. For example,the step 48 may be conducted using radiation lamps in an inertatmosphere. It should be appreciated that if a matte finish is desired,the radiation lamps can be used in an ambient atmosphere followed by aninert atmosphere. Thus, a matte finish can be superimposed on themacroscopic texture if a flatting agent is used.

It should be appreciated that process steps described in connection withFIG. 4 are equally applicable to the use of a thermally-curable coatingmixture made according to the present invention. In this case, the step40 would be directed to a thermally-curable resin and a thermalinitiator, and the step 48 would be directed to thermal curing and theformation of a thermally-cured coating.

In another embodiment of the invention, the pre-cured coating mixtureutilizes texture-producing particles to produce the macroscopic textureof the coating. These texture-producing particles may be added to thepre-cured coating mixture in the step 42. These are mixed in the samemanner as the previous embodiment, but the effective viscosity of thepre-cured coating can be much lower, typically 50-5000 cPs at a shearrate of 0.150 s⁻¹ at the application temperature, as the macroscopictexture is provided by the texture-producing particles and notnecessarily by the viscosity of the pre-cured coating mixture. It shouldbe appreciated, however, that these texture-producing particles can beused in combination with a pre-cured coating mixture that does have aneffective viscosity as well. The pre-cured coating mixture containingthese texture-producing particles is then processed in a similar mannerusing the steps 44, 46, and 48. Specifically, this pre-cured coatingmixture can be mixed in a similar manner as described above in the step44. This pre-cured coating mixture may be applied and coated on asubstrate in the step 46 using methods known in the art, including theuse of an air knife, roll coater, spray coating, curtain coating, andother coating application methods. Lastly, this pre-cured coatingmixture may be cured in a similar manner as described above in the step48.

It should be appreciated that the foregoing description of the methodsused to generate the coatings of the present invention in the context ofa radiation-cured coating is equally applicable to the generation of thethermally-cured coatings of the present invention.

FIG. 4B illustrates a cross-sectional view of a coated substrateaccording to yet another embodiment of the present invention. In thisembodiment, the coated substrate 400 is a sheet-style flooring material.This sheet flooring 400 comprises a bottom layer 401 made of felt orcellulose paper. On top of the bottom layer 401 is a gel layer 403,typically comprising a polyvinyl chloride plastisol, and on top of thisgel layer 403 is a print layer 405 that may or may not comprise ink toprovide a decorative pattern (not shown). On top of the print layer 405is a clear wear layer 407 that is typically made of a polyvinyl chlorideplastisol. On top of the wear layer 407 is a top coat 409, which may beany of the coatings of the present invention. A preferred constructionof this sheet flooring comprises a felt layer of approximately 23.5mils, a gel layer of approximately 57 mils, a print layer of nominal orrelatively small thickness, a wear layer of approximately 20 mils, and atop coat of approximately 1-1.3 mils.

The basic sheet floor manufacturing process is well known in theindustry. Generally, a felt backing is coated with a gel layer,typically a plastisol. This gel layer is then gelled to solidify it. Adecorative print may then be applied to the top of this gel layer. Theinks used in printing may be used in cooperation with the gel layer toinhibit a blowing agent that may be used in the gel layer tosubsequently enable chemical embossing of the gel layer to provideadditional aesthetics. Additionally, another plastisol-type layer may beapplied on top of the print layer to provide protection for thedecorative print or chemically embossed effects. This layer is typicallyreferred to as a wear layer, however, a topcoat may also be used on topof the wear layer to protect it from scuffing or marring. This topcoatmay be a thermal or radiation-curable coating according to any of theembodiments of the present invention.

In a preferred embodiment of the sheet floor manufacturing process, a 6to 16 feet wide felt is coated with a liquid polyvinyl chloride (PVC)plastisol (e.g., PVC resin particles dispersed in plastisizers (e.g.,phthalates)). Mixed into this liquid plastisol, which is called a gellayer, is a blowing agent (e.g., azodicarbonamide) and a catalyst (e.g.,zinc oxide). The catalyst lowers the decomposition temperature of theazodicarbonamide and increases the amount of nitrogen gas produced bythe azodicarbonamide decomposition. The liquid gel layer on felt is thengelled at a temperature below the decomposition temperature of theblowing agent (approximately 300° F.) to provide a solid non-foamed andsmooth surface for printing. After the gel layer is solidified, it isprinted with the desired design using water-based inks, thereby creatingthe print layer. In some of the inks, a compound that inhibits thedecomposition of the blowing agent is present. After the ink is printed,the PVC-coated felt is wound up and allowed to age about 24 hours. Thisaging allows the inhibitor in the ink to diffuse into the gel layer,where it is believed that the inhibitor reduces the effectiveness of thecatalyst.

The gel coated felt is then unwound on another production line where itis coated with another PVC plastisol that is formulated to be a clearlayer when solidified. This liquid layer, called the wear layer since itprotects the print from wearing, is then solidified (referred to asfused) at 385° F. for about 1.5 minutes. At this temperature, theazodicarbonamide blowing agent is activated in the gel layer resultingin the foaming of this layer which increases its thickness by forming acell structure due to the gas formation. The ratio of the gel thicknessbefore and after foaming is called the blow ratio, which is typically2:1 to 4:1. In the areas of the gel directly below the ink containinginhibitor, less foaming occurs giving less of an increase in gel layerthickness. This process results in an embossing effect (i.e., chemicalembossing). After the warm fused sheet leaves the oven it can bemechanically embossed for additional aesthetics.

While these PVC wear layers provide protection to the underlying print,they are susceptible to scuffing and marring due to the softness of thethermoplastic. To reduce the scuffing, these PVC surfaces can be eitherwaxed or coated with a thermosetting coating (known as a “no waxcoating”) such as a radiation-curable coating (e.g., urethane acrylate)or thermally-curable coating made according to the present invention. Ifthe flooring is to have a no wax finish, a radiation-curable orthermally-curable coating is then applied after the wear layer iscleaned with an acetic acid solution to remove dirt and oils. Excesscoating is applied to the wear layer using a roller, where the rollertransfers the coating from a trough to the wear layer surface. An airknife immediately meters the excess coating, where the excess isrecycled back into the trough. As partially described in Example 19, theprocess conditions of the coating application and metering such as linespeed (dwell time under the air knife), air knife pressure, angle of airknife relative to the web, gap between air knife and web, and the speedof the application roll relative to the line speed affect the coatingtexture. The uncured metered coating is then cured thermally or under UVlamps where both air and nitrogen atmospheres may be used for UV curingdepending on the gloss of the coating desired.

The degree of texture of the radiation-curable or thermally-curablecoating or top coat is dependent on the ratio of wet coating thicknessto particle diameter. In using an air knife, the air knife pressure andthe web (lined) speed are the critical parameters for achieving texture.For example, low line speed and high air knife pressure result in a verythin coating due to increased metering. When the coating containstexture-producing particles, if the coating is too thin it can not holdthe particles and a smooth non-textured coating results. If the linespeed is high and the air knife pressure is low, the coating will beless metered and apply thick. If the coating is thicker than thetexture-producing particles, the coating will be smooth. Thus, there isan optimum set of process conditions to get texture in production thatcan be determined based upon the particular pre-cured coating mixtureused.

Referring back to FIG. 3 wherein the macroscopic texture may be providedby an underlying layer in the flooring material, one embodiment of thepresent invention is the use of texture producing particles in the wearlayer of a flooring composition, such as that described in connectionwith FIG. 4B. In this embodiment, the texture is provided by the wearlayer which may then be coated with a top coating that conforms to theunderlying texture. By conforming to the underlying texture, theflooring composition will exhibit a macroscopic texture, such as aceramic-like texture where the inherently textured coating layer is thePVC wear layer in this case. Alternatively, the top coating may be madeaccording to the present invention to provide additional macroscopictexture to the flooring composition.

As noted above, the wear layer is constructed by applying PVC plastisols(dispersion of PVC particles in plastisizers) that have a viscosity ofapproximately 500-1600 cP to a printed surface (e.g., using knife overroll coating) at 10-30 mils in thickness. The plastisol is then gelledat high temperature (e.g., 300-400° F.) to form the solid, clearthermoplastic wear layer. In generating macroscopic texture withtexture-producing particles in the wear layer, the following variablesare important: (1) the type of application methods used (e.g., knifeover roll coater), (2) the high viscosity of the plastisol (typically500-1600 cP at room temperature), and (3) the thickness of the appliedwear layer (10-30 mils). By comparison, using an air knife with thelower viscosity coating containing texture-producing particles asdiscussed in previous embodiments of the present invention allows theliquid coating to be metered around the texture-producing particles togenerate the macroscopic texture. In addition, a radiation-curable orthermally-curable top coating with a lower viscosity (e.g., 50-250 cP)facilitates this metering, while the low application gauge (1-2 mils)allows fairly small particles (30-100 μm) to be used to provide texturein the coating. Therefore, to achieve texture with particles in a wearlayer, specific application methods are needed to address each of thesevariables.

In using a knife over roll coater to apply PVC plastisols, the knifeover roll coater mechanically sets the wet coating thickness, thus thetexture-producing particles in the plastisol must be smaller than thewet film thickness or streaks will be generated. Thus, to use a knifeover roll coater, texture-producing particles have to be added to theplastisol that are smaller than the wet film thickness, or the particleshave to be added after the plastisol is coated. If the texture-producingparticles are added to the plastisol before coating, these particlesmust either increase in size or change aspect ratio during gelation suchthat they protrude from the gelled wear layer to provide the macroscopictexture, or the wear layer must shrink during gelling to expose theparticles.

With regard to swelling particles, U.S. Pat. No. 5,627,231 describes aprocess of adding particles to a wear layer that swell during gelationto give the wear layer a ceramic-like texture. The particles added tothe plastisol absorb plasticizer during the gelling process and swell togive texture. However, the particles continue to absorb plasticizer andeventually become sticky. These sticky particles then attract dirt whichquickly makes the floor dirty and hard to clean. As such, an alternativewould be to utilize shrinking wear layer. Example 22 provides an exampleof a wear layer composition that shrinks thereby allowing for greaterexposure of the texture-producing particles and providing themacroscopic texture.

If the particles are to be added after knife over roll coating, theparticles can simply be wet flocked on to the surface of the coated, wetplastisol, and then gelled. This ensures that (1) the particles are onthe surface of the plastisol and, therefore, can be much smaller thanthe thickness of the wet plastisol, and (2) the particles do notinterfere with the coating application method since they are sprinkledon the wet plastisol and then the excess particles removed (i.e., wetflocking) after the plastisol is applied. Example 23 demonstrates theuse wet flocking.

To avoid the problem of mechanically setting the wet film thickness, acoating method such as air knife application can be used. However, inthe present invention it is preferred to use plastisol viscosities thatare much greater (500-1600 cP) than what is recommended for the airknife (<500 cP). When high viscosity plastisols containingtexture-producing particles arm applied by an air knife, the plastisolentraps the particles such that they are blown off the substrate leavinga smooth coating with no particles or texture. Thus, a standardplastisol must be modified to have a lower viscosity so that it can bemetered around particles. An example of a plastisol with a low viscosity(200 cP) comprises by weight, 30.8% PVC resin (75HC available fromOxychem, Dallas, Tex.), 30.8% PVC resin (567 available from Oxychem,Dallas, Tex.), 28.4% plasticizer (N-6000 available from Velsicol,Rosemont, Ill.), 4.7% plasticizer (S4375 available from Solutia, St.Louis, Mo.), 2.0% plasticizer (A-150 available from Exxon, Houston,Tex.), and 3.3% stabilizer (2347 available from OMG, Cleveland, Ohio).

As described above, the coatings of the present invention may also beutilized in connection with floor tiles. The vinyl tile manufacturingprocess and tile construction for high-end “no wax” residential tilesare different from those of vinyl sheet floor and require specializedprocess and formulation changes to achieve macroscopically textured,radiation-cured or thermally-cured surface topcoats.

In general, tiles are manufactured by calendering and/or laminationprocesses. For example, a tile base comprising, for example, limestone,is made into a continuous sheet to which a printed design and a capfilm, which is positioned on top of the printed design for protection,may be laminated. Optionally, a topcoat may then be applied to the capfilm for additional wear protection. This topcoat may be a thermal orradiation-curable coating according to any of the embodiments of thepresent invention. It should be appreciated that the general process forconstructing tiles can be used to make tiles of any thickness or size.

In a preferred tile manufacturing process, 9″ by 9″, 12″ by 12″, 14″ by14″, 16″ by 16″, and 18″ by 18″ vinyl tiles are made by first mixing PVCresin, plasticizer, pigments, and a high level (˜80%) of limestone(calcium carbonate) filler in a blender held at 115-135° F. The blendedpowder effluent is then transferred to a continuous mixer held at320-340° F. for fusion (i.e. chain entanglement) of the limestone-filledresin into thermoplastic pieces of various sizes. The thermoplasticpieces are next sent to calendering roll operations for partialsoftening and re-fusion of the limestone-filled resin into the shape ofa continuous sheet having an exiting temperature of 250-270° F. and athickness of 50-200 mils. The continuous sheet of tile base is thencarried via conveyor belt to a nip station for lamination of a printeddesign using either 2 mil thick printed PVC film or 0.5 mil thickprinted transfer paper. The latter case involves transferring the ink ofa printed design, originally on a paper roll, to the tile base at thelamination nip (the paper is subsequently removed with a re-windoperation immediately following the lamination nip).

Next, the continuous sheet of tile base and laminated print layer isconveyed to another nip for lamination of “cap film,” which is an ˜3 milthick PVC film designed to protect the print layer. Both the cap filmand print layer applications rely upon the nip pressure and incomingsubstrate temperature for lamination; the laminating rolls themselvesare not heated. For floors requiring periodic waxing, the PVC cap filmforms the uppermost layer of the manufactured tile construction (anend-user applied, sacrificial wax layer being the uppermost layer inpractice). However, for “no-wax” floors, a thermosetting topcoat isapplied to the top of the PVC cap film during manufacture and forms asurface with sufficient durability that the need for a sacrificial waxlayer is eliminated. Nevertheless, and regardless of its finaldesignation as a waxed or no-wax floor tile, the continuous sheet oflaminated tile base, print layer, and cap film is then optionallymechanically embossed and finally punched into 9″ by 9″, 12″ by 12″, 14″by 14″, 16″ by 16″, or 18″ by 18″ tiles using a metal die. The edgematerial not punched out of the continuous sheet by the die is recycledback into the tile base mixing process. The cut tiles themselves areconveyed to either a final processing and packaging station (for tilesrequiring waxing in practice) or to the topcoat application operation(for no-wax tiles).

The traditional topcoat application process for no-wax tiles involvesthe deposition and metering of a liquid film of thermally-curable orradiation-curable resin onto the tile, followed by subsequent curing ofthe resin to form a durable thermoset topcoat. The traditionallypreferred (but not exclusive) coating application method involves theuse of a curtain coater to apply and meter ˜3 mil of uncured UV-curableresin to the cap film surface of the tile. The coated, but uncured,tiles are then sent through a series of UV-processors containing UVlamps to induce cross-linking of the thermosetting resin, in the casewhere the coating is a radiation-curable coating. (Alternatively, thetiles would be heated to induce the cross-linking in the case where thecoating is a thermally-curable coating.) Final processing of most no waxtile products involves an annealing process at 110-125° F. for up to twodays to remove processing stresses and to ensure dimensional stability,as well as an edge grinding process to ensure that smooth edges arepresent for proper field installation. A thermosetting urethane backcoatis also applied with a roll-coater to balance the curling stressesimparted on the tile by the topcoat. The physical location of thebackcoater and backcoat UV-processor is usually just prior to thetopcoat operation (i.e., the backcoat is applied and cured first).

FIG. 4C is a cross-sectional view of a vinyl tile according to oneembodiment of the present invention. The tile 410 generally comprises abackcoat 412, a tile base 414, a print film or alternatively a transferprint ink (not shown), a cap film 418, and a topcoat 420 havingmacroscopic texture (not shown). In a preferred embodiment, the backcoat412 comprises a urethane backcoat of approximately 0.5-2 mils inthickness. The tile base 414 is approximately 50-200 mils in thickness,and the print film 416 is approximately 0.5 mils in thickness. The capfilm 418 comprises a PVC cap film of approximately 2.8 mils inthickness, and the topcoat 420 comprises a urethane topcoat ofapproximately 1-3 mils in thickness having macroscopic texture.

The urethane topcoat 420 may alternatively be any of the coatingsaccording to the present invention. As discussed generally above, thetopcoat resin formulation generally contains mixtures of monomers andoligomers with acrylate functional groups to serve as the cross-linkingcenters, a photoinitiator or photoinitiator package to activate thecross-linking process under the UV-lamps, flatting agents for low-glossfinishes, and various mixtures of polyurethane, polyester, and polyetherfunctional groups for imparting desired end-use performance into thecured topcoat. Moreover, the precise formulation of these ingredients istailored to maximize performance on vinyl tile, where the rigidity ofthe tile substrate relative to vinyl sheet flooring makes scratchresistance more difficult to achieve and places less emphasis onflexibility. UV-coatings for the preferred tile topcoat process mustalso be formulated to adhere to the PVC cap film, which can requiredifferent ingredients than those used for adhesion of UV-topcoats to thePVC wearlayer in sheet floor, and the coating formulation may need toform a stable curtain in the curtain coater, since curtain coating iscommonly used to apply non-textured coatings to floor tile. Lastly, theUV-processor conditions must be adjusted to produce the desired topcoatgloss (inert nitrogen atmospheres being preferred for high gloss, whilea dual air, then nitrogen, curing environment is generally required forlow gloss).

A preferred UV-curable coating formulation for use with tile substratescontains texture-generating nylon particles and alumina/silanerheological control agents. A more preferred pre-cured coating mixturecomprises, by weight, 35.303% ethoxylated trimethylolpropane triacrylate(SR 454, available from Sartomer, Exton, Pa.), 41.050% polyesteracrylate (Laromer PE56F, available from BASF, Charlotte, N.C.), 5.747%urethane acrylate (Alua 1001, available from Congoleum Corporation,Mercerville, N.J.), 0.330% acylphosphine oxide (Luceirin TPO, availablefrom BASF, Charlotte, N.C.), 8.000% 3 micron inorganic flatting agent(Acematte OK 412, available from Degussa Corp.), 2.323% prehydrolyzedsilane as an RCA coupling agent comprising 0.21%3-methacryloxypropyltrimethoxysilane (Z-6030 available from Dow Corning,Midland, Mich.), 0.015% glacial acetic acid, 0.015% deionized water, and0.07% ethanol, prehydrolyzed as described in Example 1 below, 1.000%inorganic RCA Nanotek Alumina #0100, available from NanophaseTechnologies, Burr Ridge, Ill.), and 6.250% 60 micron texture-producingparticle (Orgasol 2002 ES6, available from Atofina, Philadelphia, Pa.).As such, a preferred cured coating according to the present invention isthat coating produced using the above preferred pre-cured coatingmixture.

FIG. 4D is a process flow diagram of a process for applying a coating ofthe present invention to a tile substrate according to one embodiment ofthe present invention. In this embodiment, a radiation-curablethermosetting topcoat that providse macroscopic texture is applied to avinyl tile substrate using a novel application method. This applicationmethod is called the Roll-coat and Air-Station (RAS) process, and isused in a preferred embodiment for application of pre-cured coatingmixture to the cap film surface of a vinyl tile. The RAS process 430first involves the use of a roll-coater 432 for application and meteringof the uncured coating onto the tile substrate 431 in the form of a thinfilm having macroscopic, particle-generated texture. As describedpreviously, the aggressiveness of the macroscopic texture is dependentupon the ratio of wet film thickness to particle diameter, and thisratio is determined primarily (although not necessarily exclusively) bythis roll-coating step in the RAS process of the present invention. Fora preferred three-roll coater, the horizontal metering and transfer gaps(nips) and the vertical application gap must be carefully optimized toapply the proper amount of coating for the generation of macroscopicparticle-generated texture. If either or both of the gaps are too small,then the texture-generating particles cannot pass through the nips andare not applied to the tile substrate, which results in a smooth,non-textured coating. Conversely, if the gaps are too large, then thecoating gauge is thicker than the particle diameter and a smooth,non-textured coating is again created (i.e., the particles are buried).Macroscopically textured coatings are generated in the present inventionwhen the gaps are optimized for deposition of coatings having about thesame or slightly less film thickness than the particle; diameter (e.g.,˜1-2 mils of wet coatings containing 60 micron texture-generatingparticles).

However, the roll-coat process also imparts a directional distributionto the particle-generated textural features due to film-splittingbetween the roller and tile (see the Examples that describefilm-splitting). This directionality is generally undesirable for fieldinstallation. Thus, subsequent passage of the textured, but directional,coated tiles 434 under an air knife 436 is then required to remove theroll-coat directionality and generate more desirable uniform and randommacroscopic texture. Unlike traditional air knife coaters, the presentinvention uses air knife parameters of lip gap, gap to tile, line speed(dwell time under the air knife), and air pressure that are optimizedprimarily for the random redistribution of the roll-coat directionalityin the uncured coating and not for metering of the coating off of thetile. Moreover, a vacuum conveyor is required to hold the tile on theconveyor belt during passage under the air knife. The assemblage ofvacuum conveyor and air knife is hereafter termed the “air-station.”

It was also found that the orientation of the roll-coat directionalityrelative to the airstream direction under the air knife greatly impactsthe ability of the airstation to remove the roll-coat directionality.For example, if the tiles with uncured coating are sent under the airknife with the roll-coat directionality lines 435 parallel to theconveyor line direction (i.e., normal to the air knife slit directionand parallel to the airstream), then very little texture randomizationoccurs. However, if the tile 430 is rotated 90° relative to itsorientation upon exiting the roll-coater (i.e., the roll-coatdirectionality lines 435 are parallel to the air knife slit 437 andnormal to both the conveyor line direction and the air knife airstream438), then the airstation can much more easily randomize theparticle-generated texture. By readjusting the airstation parameters itwas also possible to randomize the texture with a 45° tile rotation 439,which implies that simply mounting the air knife at 45° relative to theairstation conveyor will eliminate the need for actual rotation of thetiles in a continuous production process.

It should be appreciated that in the use of a roll-coating process,particularly with multiple rolls, it is desirable that the roll incontact with the substrate is a soft durometer roll to meter the coatingmixture into the embossed areas or regions of the substrate, such as anembossed tile or sheet flooring or other embossed substrate. An exampleof this is described in Example 25.

It should be appreciated that the roll coating process and the air knifeprocess may also be used separately for coating tiles. In addition, itshould be appreciated that although the foregoing methods described foruse in the manufacture of coated tiles, these methods may also be usedin applying the pre-cured coating compositions of the present inventionto sheet flooring as well. Specifically, the RAS process may be used forsheet flooring, other flooring substrates, and non-flooring substrates.Further, the roll coating process alone and spray coating alone may beused to coat tiles, sheet flooring, other flooring substrates, andnon-flooring substrates.

FIG. 4E shows a cross-sectional view of another embodiment of thepresent invention. The tile 440 generally comprises a backcoat 442, atile base 444, a print film 446 or alternatively a transfer print ink(not shown), a cap film 448, an undercoat 450, and a topcoat 452 havingmacroscopic texture 454. It should be appreciated that the diagrammaticrepresentation of the macroscopic texture 454 should not be deemedlimiting and is simply used to represent the macroscopic texture. In apreferred embodiment, the backcoat 442 comprises a urethane backcoat ofapproximately 0.5-2 mils in thickness. The tile base 444 isapproximately 50-200 mils in thickness, and the print film 446 isapproximately 0.5 mils in thickness. The cap film 448 comprises a PVCcap film of approximately 2.8 mils in thickness, and the undercoat 450comprises a radiation or thermally cured undercoat of approximately 1-3mils in thickness. The topcoat 452 comprises a radiation or thermallycured topcoat of approximately 0.1-3 mils in thickness havingmacroscopic texture.

In this particular embodiment, there is a double layer ofradiation-cured top coats, which provides improved scratch resistance.Such double-layer topcoats require a partial cure of the undercoat togive the undercoat sufficient structural integrity to withstand the RASprocess used in application of the textured upper coat. However, if theundercoat approaches a fully cured state prior to application of thesecond, textured coating, then the textured upper coat will not properlyadhere to the undercoat. Careful control of cure conditions during thepartial cure of the undercoat is, therefore, required. After thetextured upper coating has been applied on top of the partially curedundercoat via the RAS process, normal low or high gloss curing is thenused to fully cure the entire double-layer topcoat system.

The invention having been described, the following examples illustratevarious embodiments and features of the present invention. It should beappreciated that the following examples are presented to illustrate,rather than to limit, the scope of the invention.

Example 1

This example describes a microscopic, texture with good abrasionresistance, but poor cleanability. 60 g of alumina (available asNanotek® alumina 0100 from Nanophase Technologies Corp., Burr Ridge,Ill.) having an average particle diameter range. of 27-56 nm, 7.92 g ofprehydrolyzed 3-methacryloxypropyltrimethoxysilane (available as Z-6030from Dow Corning, Midland, Mich.), 240 g of a UV-curable resin (seeTable 1 below for the resin composition), and about 200 g of 0.5 in.diameter porcelain balls were added to a porcelain media mill.

The mixture was ball milled for about 6 hours at room temperature. Thepre-cured coating mixture, after removal of the grinding media, wasapplied using a 1.5 mil draw bar to rigid polyvinyl chloride floor tilesubstrates at room temperature. The tile substrates were then UV-curedin a two step process. First, the tile substrates were UV-cured in airusing a line speed of 100 feet per minute (fpm) under two H-bulb(mercury) lamps on high. Then the tile substrates were UV-cured innitrogen (<500 ppm oxygen) using two H-bulbs set on low and a line speedof 20 fpm. The coated tiles were subjected to this latter inertUV-curing step a second time. The resulting coatings were transparentwith an extremely low gloss of 6% (at 60°). Scanning Electron Microscopy(SEM) images of this coating indicate that microscopic wrinkling waspresent, i.e., micro-wrinkling. A Taber scratch test consisting ofscribing 5 concentric circles on the coated samples with a metal stylusweighted from 300 to 500 g in 50 g increments yielded no visiblescratches on the coating surface. A qualitative scratch rating systemwas used to evaluate the scratches from the test (i.e., a 0-7 scale wasused, where 7 is the best in that there are no visible scratches), andthis coating was rated 7. When this coating was exposed to heavy trafficareas, it picked up dirt particles quite easily and was very difficultto clean.

TABLE 1 UV-Curable Resin Composition Component Manufacturer Wt %Urethane acrylate (Alua 1001) Congoleum (Mercerville, NJ) 53.4Ethoxylated diacrylate (SR 259) Sartomer (Exton, PA) 8.8 Propoxylateddiacrylate (SR 306) Sartomer (Exton, PA) 24.3 Ethoxylatedtrimethylolpropane Sartomer (Exton, PA) 13.4 triacrylate (SR 454)Acylphosphine oxide (Luceirin BASF (Charlotte, NC) 0.1 TPO)

As noted above, prehydrolyzed silane was used. The silane (Z-6030) wasto prehydrolyzed to make it more reactive with the surface of thenanometer-sized alumina. The prehydrolysis was conducted by first mixingat room temperature 5 g of glacial acetic acid, 5 g of deionized water,and 25 g of ethyl alcohol. Then, 75 g of Z-6030 were added to themixture. The mixture was gently agitated for about 24 hours. The mixturewas allowed to stand several days before use.

Example 2

This example shows a coating with macroscopic texture having goodcleanability and scratch resistance. 31.17 g of silica (available asNanotek® silica 2000 from Nanophase Technologies Corp., Burr Ridge,Ill.) having an average particle diameter range of 15-33 nm, 10.51 g ofprehydrolyzed 3-methacryloxypropyltrimethoxysilane (available as Z-6030from Dow Corning, Midland, Mich.) prepared as described in Example 1,100 g of a UV-curable resin (see Table 2 below for resin composition).The mixture was hand stirred with a wooden spatula and then mixed withan ultrasonic probe for about 20 minutes. The pre-cured coating mixturewas applied to flexible polyvinyl chloride floor substrates at roomtemperature with a spatula and distributed on the substrate with an airknife. These sheet vinyl substrates were then UV-cured under nitrogen(<500 ppm oxygen) using two H-bulbs set on high and a line speed of 100fpm. Two passes under the lamps were made under these conditions. Theresulting coating was transparent with a gloss value (at 60°) of about11%. The coating also had a macroscopic wave-like texture and was foundto be cleanable. A Taber scratch test consisting of scribing 5concentric circles on the coated samples with a metal stylus weightedfrom 300 to 500 g in 50 g increments yielded no visible scratches on thecoating surface. Using the qualitative scratch rating system, thiscoating was rated a 7.

TABLE 2 UV-Curable Resin Composition Component Manufacturer Wt %Urethane acrylate (Alua 1001) Congoleum (Mercerville, NJ) 53.4Ethoxylated diacrylate (SR 259) Sartomer (Exton, PA) 8.8 Propoxylateddiacrylate (SR 306) Sartomer (Exton, PA) 24.2 Ethoxylatedtrimethylolpropane Sartomer (Exton, PA) 13.3 triacrylate (SR 454)Surfactant (DC 193) DOW Corning (Midland, MI) 0.1 Acylphosphine oxide(Luceirin BASF (Charlotte, NC) 0.2 TPO)

Example 3

To show the benefits of using nanometer-sized alumina in a coatingaccording to the present invention, a coating was made using largeralumina particles. 60 g of alumina (available as A152-SG from Alcoa,Pittsburgh, Pa.) having an average particle diameter of 1.5 μm, 0.48 gprehydrolyzed silane (Z-6030), 240 g of the resin used in Example 1, andabout 200 g of 0.5 in. porcelain balls were added to a ball mill andmilled as in Example 1. This pre-cured coating mixture was applied,cured, and tested for scratch resistance as given in Example 1. Theresulting coating was visually not as transparent as the coating inExample 1 and was given a scratch rating of 2 indicating visualscratches were present.

Example 4

Tests were conducted to determine the effects of silane as a couplingagent on the dispersion of nanometer-sized alumina 2 g of Nanotek®alumina 0100 having an average particle diameter range of 27-56 nm wasadded to 10 g of each of the following liquids: ethoxylated diacrylate(available as SR 259 from Sartomer, Exton, Pa.), propoxylated diacrylate(available as SR 306 from Sartomer, Exton, Pa.), ethoxylatedtrimethlolpropane triacrylate (available as SR 454 from Sartomer, Exton,Pa.), and urethane acrylate (available as Alua 1001 from Congoleum,Mercerville, N.J.). The mixtures were stirred, shaken, and then placedinto an ultrasonic bath for 30 minutes. To some of these mixtures 0.24 gprehydrolyzed silane, as prepared in Example 1, was added, and themixture was stirred. The consistencies of each of these mixtures aredescribed in the Table 3 below.

TABLE 3 Effects of Prehydrolyzed Silane Liquid Dispersing AgentObservations SR 306 none thixotropic paste silane low viscosity liquidSR 259 none low viscosity liquid silane low viscosity liquid SR 454 nonethixotropic paste silane low viscosity liquid Alua 1001 nonenon-thixotropic cream silane low viscosity liquid

The observations show that the urethane acrylate and the Ethoxylateddiacrylate disperse the nanometer-sized alumina better than thepropoxylated diacrylate and the Ethoxylated trimethlolpropanetriacrylate. These observations also show that the addition of theprehydrolyzed silane dispersing agent improves the dispersion of thenanometer-sized alumina.

Example 5

This example shows the effects of alumina size and coupling agent on theclarity of the cured coating. The pre-cured coating mixture in Example 1was prepared in the identical manner described with the followingexception: the prehydrolyzed silane was prepared using 75 g of ethanolinstead of 75 g of Z-6030 silane. Thus, this pre-cured coating mixturecontained no coupling agent. This pre-cured coating mixture (referred toas Example 5), the pre-cured coating mixture in Example 1, and thepre-cured coating mixture in Example 3 were applied at room temperatureusing a 3 mil draw-down bar to glass substrates. The drawn downpre-cured coating mixtures were then cured using two curing conditionsas described in Table 4.

TABLE 4 UV-Curing Conditions Condition Parameters 1 atmosphere = airline speed = 100 feet per minute (fpm) lamp = 2 H-bulb (mercury) lampson high passes = 1 atmosphere = nitrogen (<500 ppm oxygen) line speed =20 fpm lamp = 2 H-bulb lamps on low passes = 2 2 atmosphere = nitrogenline speed = 20 fpm lamp = 2 H-bulb lamps on low passes = 2

The percent haze is defined as follows:

% haze=(100−% specular transmission)/% total transmission

and was determined for these cured coatings using a CHROMA SENSOR CS-5from Applied Color Systems, Inc. and a method similar to ASTM D 1003-92.The thicknesses of the detached coatings were determined with a MADAKEmicrometer. The haze and thickness values are given in Table 5 below.

TABLE 5 Coating Thickness and Haze Results % Coating Cure ConditionsThickness (mil) Haze Example 1 1 2.6 59.3 (20% nano-sized alumina)Example 1 2 2.6 67.3 (20% nano-sized alumina) Example 3 1 3.2 99.4 (20%micron-sized alumina) Example 3 2 3.2 99.4 (20% micron-sized alumina)Example 5 1 1.7 82.0 (20% nano-sized alumina, no silane) Example 5 2 6.397.8 (20% nano-sized alumina, no silane)

The percent haze values show that the coating with nanometer-sizedalumina was much less hazy than the coating containing micron-sizedalumina regardless of cure conditions. The data also show that thesilane coupling agent improves the clarity of the coatings containingnanometer-sized alumina.

Example 6

This example shows the effects of inorganic particle type and loading onthe cured coating texture. Six pre-cured coating mixtures were preparedwhere the inorganic nano-particles and the prehydrolyzed silane (asdescribed in Example 1) were added to the UV-curable organic phase usedin Example 2. Each pre-cured coating mixture was mixed with a Cowlesblade and then an ultrasonic probe. The composition of these pre-curedcoating mixtures is shown in Table 6.

TABLE 6 Pre-Cured Coating Mixture Compositions Pre-Cured Wt % Photo-Coating Nanometer- Prehydrolyzed initiator Mixture Sized Particle Wt%/Vol % Silane (%) 1 None 0/0 0 0.1 2 Al₂O₃ 19.5/6.0  1.8 0.1 3 Al₂O₃28.9/10   2.6 0.1 4 Al₂O₃   40/15.4 3.6 0.2 5 SiO₂  11/5.5 2.5 0.1 6SiO₂  16/8.3 3.7 0.2 7 SiO₂   22/11.8 5.1 0.2

These pre-cured coating mixtures were then applied to flexible vinylflooring substrates which were cleaned with a solution of acetic acid,soap, and water. The pre-cured coating mixtures were applied at roomtemperature using a pipette or a spatula depending on the viscosity, andthen the samples were passed through an air knife to distribute thepre-cured coating mixture over the substrate and to remove any excess.The resultant films were then cured under UV lamps using different lampintensities and atmospheres as described in Table 7 below. Scanningelectron microscopy (SEM) images of the coatings were taken along withgloss measurements at 60°.

TABLE 7 Gloss and Texture Measurements Gloss Texture Coating CureConditions (%) (SEM/visual) 1 N₂ - 100 fpm, 2 lamps high, 2 passes 80smooth Air - 100 fpm, 2 lamps high 6 long micro- N₂ - 100 fpm, 2 lampshigh, 2 passes wrinkles 2 N₂ - 100 fpm, 2 lamps high, 2 passes 80 smoothAir - 100 fpm, 2 lamps high 4 short micro- N₂ - 100 fpm, 2 lamps high, 2passes wrinkles 3 N₂ - 100 fpm, 2 lamps high, 2 passes 60 some macrotexture Air - 100 fpm, 2 lamps high 30 very short micro- N₂ - 100 fpm, 2lamps high, 2 passes wrinkles 4 N₂ - 100 fpm, 2 lamp high, 2 passes 30macro texture Air - 100 fpm, 2 lamps high 30 macro texture N₂ - 100 fpm,2 lamps high, 2 passes 5 N₂ - 100 fpm, 2 lamp high, 2 passes 20 macrotexture Air - 100 fpm, 2 lamps high 5 macro texture and N₂ - 100 fpm, 2lamps high, 2 passes micro-wrinkles 6 N₂ - 100 fpm, 2 lamp high, 2passes 17 macro texture Air - 100 fpm, 2 lamps high 16 macro textureN₂ - 100 fpm, 2 lamps high, 2 passes 7 N₂ - 100 fpm, 2 lamp high, 2passes 6 macro texture Air - 100 fpm, 2 lamps high 6 macro texture N₂ -100 fpm, 2 lamp2 high, 2 passes

Coatings cured under both air and inert atmospheres having 30% or lessnanometer-sized alumina showed micro-sized wrinkles, which looked likespaghetti in the SEM images (200×). As the concentration of alumina isincreased from 0 to 20%, the length of the wrinkles decreases underinert (N₂) curing conditions. At 30% alumina, the wrinkle length isquite small resulting in a surface resembling a golf ball surface in theSEM images. At 40% alumina, the micro-wrinkling is not observed in theSEM (surface is smooth), but a macro wave-like texture is observed withthe naked eye. Wave-like macro texture is also observed with thecoatings having 16% and 22% silica. In the cases where micro-wrinklingis not observed, the macro texture observed is independent of the cureconditions (two zone versus one zone) used.

Example 7

This example demonstrates that wave-like macroscopic texture isgenerated by the coating application method. Pre-cured coating mixture 5in Example 6 above was applied to a substrate with an air knife as inExample 6. The same pre-cured coating mixture was also applied to asecond substrate with a 1.5 mil draw down bar. Both samples were curedin the inert atmosphere as described in Example 6. The sample coatedwith a draw bar had a visibly smooth surface and a gloss of 74% comparedto a wave-like visible texture with a gloss of 20% for the sample coatedwith an air knife.

Example 8

This example shows the effect of shear rate and temperature, on thepre-cured coating viscosity. The viscosities of pre-cured coatingmixtures 3 (28.9% alumina) and 4 (40% alumina) from: Example 6 weremeasured using a Brookfield viscometer (model DV-II, RV) with spindles21 and 29 as a function of spindle rotation rate (related to shear rate)and temperature. FIG. 5 shows the results of these measurements forpre-cured coating mixture 3 and FIG. 6 shows the results for pre-curedcoating mixture 4. The data show that the pre-cured coating mixtureviscosity decreases with temperature and shear rate. The viscositydependence with shear rate indicates that the actual viscosity of thepre-cured coating during application with an air knife is probably lessthan when measured at low shear (0.150 s⁻¹) by the Brookfield, since theshear rate under the air knife is assumed to be greater than 0.150 s⁻¹.The viscosity dependence on temperature demonstrates the importance ofkeeping the pre-cured coating at the required temperature duringapplication, since too high of a temperature may result in a coatingthat does not produce macroscopic texture because the viscosity is toolow. The difference in the curves between FIGS. 5 and 6 show that theamount of RCA in the pre-cured coating influences the coating rheology,which could control the type and degree of texture in the cured coating.

Example 9

This example shows the effects of pressured coating viscosity on curedcoating texture. Using the pre-cured UV resin described in Table 2, 20%,22.5%, 25%, 27.5%, and 30% nanometer sized alumina (as described inExample 1) was added and mixed with a Cowles blade mixer. Additionally45% of nanometer-sized calcium carbonate was added to the resindescribed in Table 2 and mixed with a Cowles blade mixer. Theviscosities of these pre-cured coatings were measured as described inExample 8 and are given in Table 8. These pre-cured coatings were thenapplied to flexible sheet vinyl substrates and coated with an air knifeat room temperature. In the case of the coating with 45% calciumcarbonate, the pre-cured coating simply blew off the substrate when theair knife was used. The samples were cured under inert conditions andtested for scratch resistance (Taber) and the gloss was determined.These data are also given in Table 8.

TABLE 8 Pre-Cured Coating Viscosity Effects on Cured Coating PropertiesViscosity (cPs) at 0.150 s⁻¹ at Room Gloss Macroscopic Scratch CoatingTemperature (%) Texture (Taber) 20% alumina 30,000 46 none some visible22.5%   56,667 37 very slight some visible 25% 110,000 25 yes somevisible 27% 173,000 19 yes some visible 30% 408,000 9 yes, most nonevisible aggressive 45% calcium 1,230,000 n/a n/a n/a carbonate

These data indicate that for the air knife conditions presently used,the viscosity of the coating needs to be approximately in the range of100,000-1,000,000 cPs measured at room temperature (at a shear rate of0.150 s⁻¹) in order to generate macroscopic texture. The data alsoindicate that more aggressive texture yields better scratch resistance.

Example 10

This example shows the effect of aging and prehydrolyzed silaneconcentration on the pre-cured coating viscosity. The viscosity ofpre-cured coating mixture 4 in Example 6 (40% alumina) was determined asa function of time. These results are shown in FIG. 7. The pre-curedcoating mixture viscosity was found to have an aging effect in whichfresh samples change viscosity over a period of about one week beforeleveling at a new viscosity. Specifically, pre-cured coating mixturesprepared with the optimal prehydrolyzed silane concentration (10μmol/m²) decrease about 25% in viscosity after 10 days and change colorfrom a dark gray to a lighter gray, whereas pre-cured coating mixtureswith 20 μmol/m² increase in viscosity by more than 4 times (i.e., theinitial value was 75% lower than final value) in the same time period.This behavior suggests that at and below the optimal prehydrolyzedsilane concentration the prehydrolyzed silane is continuing to furtherdisperse the alumina particles as the prehydrolyzed silane moleculesdiffuse slowly to their final equilibrium locations on the particlesurfaces and react with Al—OH groups. Conversely, when excessprehydrolyzed silane is present the equilibrium favors reagglomerationand crosslinking by prehydrolyzed silane condensation but is apparentlykinetically limited prior to equilibration. Both processes scan toinvolve rather slow kinetic and/or diffusive steps and arm unlikely tobe affected much by additional mechanical mixing.

Example 11

The effect on pre-cured coating viscosity of the concentration ofprehydrolyzed silane coupling agent (as prepared in Example 1) wasdetermined by measuring the viscosity as in Example 8 of a pre-curedcoating mixture containing 40% nanometer-sized alumina (e.g., thepre-cured coating mixture 4 in Example 6 except the silane level wasvaried). The amount of prehydrolyzed silane used in all the examples wascalculated using the following equation:

M _(ps)=(10⁻⁶ MW _(ps) as _(np) m _(np))/C _(ps)

where M_(ps) is the mass of prehydrolyzed Z-6030 (in g), a is the numberof active sites on the nano-particle (in μmole/m²), MW_(ps) is themolecular weight of the prehydrolyzed Z-6030 (234 g/mol), s_(np) is thenanometer-sized particle surface area (in M²/g), m_(np) is the mass ofnanometer-sized particles used in the formulation (in g), and C_(ps) isthe weight fraction of prehydrolyzed silane in the solution (fromExample 1, typically 0.6818). Based on Parker et al., Mat. Res. Symp.Proc. 249 (1992) 273, 10 μm of active sites/m² of inorganic in all ofthe samples was used, because it should give the lowest pre-curedcoating mixture viscosity and, hence, the best dispersion of thenanometer-sized particles. However, it should be appreciated that bycontrolling the amount of prehydrolyzed silane (more or less than 10μmole/m²) can result in different shear dependent rheology, which inturn could lead to different textures.

The pre-cured coating mixture viscosity was measured as a function ofprehydrolyzed silane level (represented by the “a” value as describedabove) and the results are shown in FIG. 8. These data show that at agiven strain rate, the pre-cured coating mixture equilibrium viscositywas found to initially decrease as the silane concentration wasincreased, presumably due to enhanced dispersion of the nanometer-sizedparticles in the resin phase. A viscosity minimum was reached atapproximately 10 μmol silane/m² Al₂O₃ and serves as a measure of optimaldispersion for this surfactant-inorganic-resin mixture (in agreementwith sedimentation results obtained by Parker et al. for then-octyltriethoxysilane-toluene-5 μm Al₂O₃ system). The increase inviscosity observed at slightly higher silane concentrations corresponds,to some reagglomeration of alumina particles as the excess silane formslarger organo-phobic phase domains (domains that include both thealumina particles and the hydrophilic ends of the silane molecules) thatminimize surface energies between phases. Finally, viscosity againdecreases at much higher silane concentrations due to simple mixing-rulebehavior.

Example 12

This example demonstrates the use of an organic RCA. 20 g of an organic(castor wax derivative) RCA Thixcin R (Rheox Inc., Hightstown, N.J.) wasadded to 480 g of the pre-cured UV resin described in Table 2 and mixedwith a Cowles blade mixer. The mixture was then heated at 70° C. untilthe Thixcin R dissolved. The mixture was then allowed to cool to roomtemperature. The viscosity of this mixture at a shear rate of 0.150 s⁻¹at room temperature was 243,000 cPs. This mixture was then coated onflexible sheet vinyl using an air knife and cured under inertconditions. The resulting cured coating was transparent and had awave-like macroscopic texture. When scratched using the Taber scratchtest, no visible scratches were observed.

Example 13

This example demonstrates the use of both an organic RCA and aninorganic flatting agent. 12 g of Thixcin R organic RCA and 19.14 g ofAcematte OK 412 (Degussa Corp.) silica flatting agent were added to 288g of the pre-cured UV resin described in Table 2 and mixed as in Example12. This mixture was coated on a flexible vinyl sheet floor with an airknife and cured under both atmospheric and inert conditions. Theresulting coating had a matte finish and wave-like texture.

Example 14

This example shows that wave-like macroscopic texture can be generatedwithout the use of an RCA. 85.25 g of Alua 2302 and 21.31 g Alua 1001urethane acrylate oligomers (Congoleum Corp., Mercerville, N.J.), 66.14g of Actilane 424 and 26.64 g of Actilane 430 acrylate monomers (AkcrosChemicals, New Brunswick, N.J.), 0.2 g DC 193 surfactant, and 0.394 g ofLuceirin TPO photoinitiator were added to a container at roomtemperature. This mixture was heated to 70° C. and mixed with a Cowlesblade mixer. After cooling to room temperature, the pre-cured coatingmixture was applied to flexible vinyl substrates, coated with an airknife, and UV-cured under inert conditions. The resulting coating wastransparent and had macroscopic wave-like texture.

Example 15

This example demonstrates the use of organic texture-producing particlesand an inorganic flatting agent. 6.25 g of Orgasol 2002 ES 6 NAT(Atofina, Philadelphia, Pa.) polyamide 12 texture-producing particle (60μm in diameter) and 5.625 g of Acematte OK 412 flatting agent (3 μmdiameter) were added to 88.125 g of the preset UV-resin described inTable 2 and mixed with a Cowles blade mixer. This mixture was heated to70° C. and coated on a flexible sheet vinyl floor using an air knife.The pre-cured coating was cured at a line speed of 100 fpm usingatmospheric and then inert conditions. The resulting coating wastransparent coating with a matte finish and sandpaper-like texture.

Example 16

This example shows the effects of the size of the texture-producingparticles on the cured coating texture. Four pre-cured coating mixtureswere prepared as in Example 15 where 6.25% of Orgasol 2002 polyamide 12texture-producing particles was added to the pre-cured UV-resindescribed in Table 2. The four mixtures differed in that each containeda different sized particle of Orgasol 2002: 30 μm (grade ES 3), 40 μm(grade ES 4), 50 μm (grade ES 5), and 60 μm (grade ES 6). Each mixturewas applied at 70° C. to sheet vinyl and coated with an air knife. Allcoatings were UV-cured under inert conditions. The cured coatingcontaining the 30 μm particles had a visibly fairly smooth surface witha matte finish. The coatings with the larger particles had progressivelymore visible texture as the particle size increased, where the 60 μmparticles gave the most visible and aggressive (largest texturalfeatures) texture. The scratch resistance of the coatings improved withincreasing particle size, where 60 μm showed almost no visible scratchesafter the Taber scratch test. FIG. 9 is a photograph of the top of aportion of the coated substrate produced using the 60 μm particles, andFIG. 10 is a photograph of the top of a portion of the coated substrateproduced using the 40 μm particles. The difference in the aggressivenessof the texture is evident. It should be appreciated, however, that theconcentration of particles used would also be expected to have aninfluence on textural aggressiveness.

For illustrative purposes, “traces” of the surface textures of thesesamples were obtained by rubbing a soft graphite pencil over translucenttracing paper that was itself placed on top of the textured surfaces.The traces were then digitally scanned. FIG. 11 shows the texture of thecoating producing using the 60 μm particles, and FIG. 12 shows thetexture of the coating produced using the 40 μm particles. The tracesclearly show the decrease in textural aggressiveness as nylon particlesize is decreased from 60 μm as shown in FIG. 11 to 40 μm in FIG. 12.

These traces also allow for estimation of certain features of thetexture. FIG. 13 is an illustration of the general type of macroscopictexture produced by the coatings in this Example 16. As shown, threeparameters, a, b and c, are defined to describe certain planar featuresof the texture. These parameters are defined as follows: “a” representsthe distance between peaks of the texture, “b” represents the width ofeach textural feature, and “c” represents the length of each texturalfeature. These parameters were measured manually from the correspondingtraces and, therefore, may have substantial inherent error associatedwith them; however, they can be used to distinguish gross differencesbetween the textures. Regardless, these parameters should not be viewedor used as limiting the type, shape, or size of the macroscopic texture.The ranges for these parameters for the coatings produced in thisExample 16 are as follows: for the coating made with 60 μm particles aranges from 10-50 mils, b ranges from 5-30 mils, and c ranges from100-350 mils, for the coating made with 40 μm particles a ranges from5-30 mils, b ranges from 1-20 mils, and c ranges from 10-150 mils, andfor the coating made with 30 μm particles a ranges from 5-20 mils, branges from 1-10 mils and c ranges from 1-50 mils.

The average gloss values (60°) and the textural relief values (definedas maximum coating thickness minus minimum coating thickness) were alsomeasured for the coatings produced by this Example 16. The gloss valuesare 10.8, 16.9, and 35.3 for the coatings made with 60 μm, 40 μm, and 30μm particles, respectively. The textural relief values are 1.99 mils,0.52 mils, and 0.29 mils for the coatings made with 60 μm, 40 μm, and 30μm particles, respectively.

Example 17

This example describes textured coatings. containing organictexture-producing particles, an inorganic RCA with a coupling agent, andboth organic and inorganic flatting agents. Per-cured coating mixtureshaving the composition shown in Table 9 were mixed with a Cowles blademixer.

TABLE 9 Pre-Cured Coating Mixture Compositions in Weight PercentComponent Coating A Coating B UV-Curable Resin from Table 2 85.62 85.95Orgasol 2002 ES 6 (60 μm texture-producing 6.12 6.25 particle) Orgasol2001 UD (5 μm organic flatting agent) 6.0 0 Acematte OK 412 (3 μminorganic flatting agent) 0 5.49 Nanotek Alumina (inorganic RCA) 1.96 2Prehydrolyzed Z-6030 (coupling agent from 0.30 0.31 Example 1)Both coatings were applied to flexible sheet vinyl at 70° C. and coatedwith an air knife. These coated substrates were UV-cured underatmospheric and then inert environments. The resulting cured coatingswere transparent and had sandpaper-like macroscopic texture and mattefinishes.

Example 18

This example demonstrates the use of a roll coater application methodfor generating and controlling macroscopic texture similar to that ofwood-grain. Three pre-cured coating mixtures were used, including thecoating of Example 9 (30% nano-alumina inorganic RCA), the coating ofExample 12 (organic RCA), and the coating of Example 16 (60 μmtexture-generating nylon particles). These pre-cured coating mixtureswere then applied to cleaned, semi-rigid vinyl tile flooring. substratesusing a pipette or spatula as described in Example 6. Distribution ofthe pre-cured coating mixture to a macroscopically textured state andremoval of excess coating was then achieved by passing the samples undera contacting roller using the process conditions listed in Table 10.Specifically, Table 10 gives the conditions for the contacting, roll,which actually makes contact with and the pre-cured coating to providemacroscopic texture. More specifically, the contacting roll acts tosplit the pre-cured coating mixture that has been applied to thesubstrate between the contacting roll and the substrate and is referredto as “film-splitting,” where “film” refers to the pre-cured coatingmixture as applied to the substrate. This film-splitting phenomenon actsto form the macroscopic texture of the coating on the substrate. The gapindicated is between the contacting roll and the uncoated substratesurface when the uncoated substrate is between the rolls (i.e., totalgap minus substrate thickness). Also, in the case where the contactingroll is rotating, the rotation is away from the surface of the sample.In all cases, the lower roll carried the samples between the rolls at100 fpm and, upon exiting the roll coater, the pre-cured coated sampleswere cured under an inert (N₂) environment at 100 fpm.

TABLE 10 Roll Coated Sample Compositions and Process Conditions Sampleand Figure Process Identification Coating Conditions 1 Organic RCACoating Hard rubber roll (stationary) (FIGS. 15 and 19) of Example 12Gap = 4.0 mils 2 Inorganic RCA Hard rubber roll (stationary) (FIGS. 14and 20) Coating of Gap = 4.0 mils Example 9 3 Organic RCA Coating Hardrubber roll (stationary) (FIGS. 16 and 21) of Example 12 Gap = −10 mils(compressed) 4 Inorganic RCA Soft rubber roll (FIGS. 17 and 22) Coatingof (rotating 100 fpm) Example 9 Gap = 0.0 mils 5 Texture-Generating Hardrubber roll (stationary) (FIGS. 18 and 23) Particles Coating Gap = 18mils of Example 16

FIGS. 14-18 are photographs of the top of a portion of each coatedsubstrate made using coatings 1-5 listed in Table 10. FIGS. 19-23 aretraces, made as described in Example 16, of the surface textures ofthese coated substrates having coatings 1-5 listed in Table 10. Gloss(60°) and gauge (thickness) measurements are given in Table 11, wheretextural relief is calculated as the maximum gauge minus the minimumgauge (in mils). Note that the gloss is reported for both the in-linedirection (i.e., the direction that the sample traveled while passingthrough the roll coater) and for the transverse direction. Gaugemeasurements were made using a light microscope equipped with amicroscale and involved viewing cross-sections of the cured samples cutin the transverse direction.

FIG. 24 illustrates the general type of macroscopic texture produced bythe coatings in this Example 18, and FIG. 25 is an enlarged view of aportion of FIG. 24. As shown, the texture produced in this Example 18can be described as “branched”. FIGS. 24 and 25 show three parameters,a, b and c, that are defined to describe certain planar features of thetexture. These parameters are defined as follows: “a” represents thedistance between branches of the texture, “b” represents the width ofeach branch, and “c” represents the length of each branch. Theseparameters were measured manually from the traces for each of thecoatings shown in FIGS. 19-23 and, therefore, may have substantialinherent error associated with them; however, they can be used todistinguish gross differences between the textures. Regardless, theseparameters should not be viewed or used as limiting the type, shape, orsize of the macroscopic texture. The ranges for these parameters for thecoatings produced in this Example 18 are provided in Table 11.

TABLE 11 Gloss and Texture Measurements of Roll Coated Samples Range ofPlanar Gloss (60°) Gauge (mils) Dimensions (mils) Sample In-line Trans.Min Max Relief (mils) a b c 1 50.2 15.5 1.20 2.44 1.24  40-100 10-20100-1500 2 69.3 21.2 1.35 2.34 0.99  40-100 10-20 100-1700 3 65.8 29.20.69 1.11 0.42 20-30  5-10 100-1000 4 32.1 16.4 1.08 2.69 1.61 40-7010-20 100-200  5 27.6 17.4 0.79 1.71 0.92 40-70 20-40 300-500 

These results show that a range of texture similar to that of wood-grainmay be achieved by adjustment of process conditions during the rollcoating application of the pre-cured coating mixtures. Key parametersappear to be the rotational speed of the contacting roll that directlycontacts the pre-cured coating, the gap between the contacting roll andthe sample, and the hardness of the contacting roll.

If the contacting roll is moving in the line direction, then thepre-cured coating film is split quickly as the moving roll pulls afraction of the coating away from the coated substrate. This results invery short textural branches (sees for example, FIG. 18). Conversely, astationary contacting roll does not split the film as rapidly, allowingthe branches to extend to much longer lengths before a fraction of thebranching film detaches from the substrate and ends the branch. Thismacroscopic texture is best described as “wood-grain” in nature.Moreover, the wood-grain texture may be further controlled by adjustingthe gap. A smaller gap yields a more finely scaled wood-grain texture(e.g., compare FIGS. 19 and 21). The use of texture-producing particlesin a roll-coated pre-cured coating mixture produces a hybrid macroscopictexture that contains both wood-grain and “sandpaper-like” texturalelements (see, for example, FIGS. 18 and 23). The hardness of thecontacting roll is also expected to affect the film splitting behaviorof the roll-coating application method, as are intrinsic pre-curedcoating properties such as viscosity and particle density.

Example 19

This example illustrates how the manipulation of process conditions maybe used to control the aggressiveness of macroscopic texture generatedby an air knife coating application method. Two pre-cured coatingmixtures were used, the first being the coating of Example 9 (30%nano-alumina inorganic RCA). The second pre-cured coating consisted ofthe coating composition given in Example 15, with the exception that theorganic text generating particles were 40 μm polypropylene particlesadded at 5 wt % (Propyltex 200S available from Micro Powders, Inc.,Tarrytown, N.Y.) instead of the 625 wt % nylon particles. Thesepre-cured coating mixtures were applied to flexible sheet vinyl floorwith an air knife using the process conditions indicated in Table 12.The pre-cured coated samples were then cured under an inert (N₂)environment at 100 fpm.

TABLE 12 Air Knife Coater Sample Compositions and Process ConditionsSample and Figure Identification Line Speed Air Knife Pressure InorganicRCA Coating 1 (FIGS. 26 and 29) 100 4.0 2 (FIGS. 27 and 30) 50 4.0 3(FIGS. 28 and 31) 10 4.0 Particle Coating 4 100 4.0 5 10 4.0 6 100 1.5 710 1.5

FIGS. 26-28 are photographs of the top of a portion of each coatedsubstrate, made using coatings 1-3 listed in Table 12, respectively.FIGS. 29-31 are traces, made as described in Example 16, of the surfacetextures of these coated substrates having coatings 1-3 listed in Table12, respectively. These figures show that the macroscopic textureproduced using the inorganic RCA are wave-like. Traces of the particletextures for samples 4-7 in Table 12 were not made, but traces ofsimilar particle-generated “sandpaper” macroscopic texture can be foundin Example 16.

FIG. 32 is an illustration of the general type of wave-like macroscopictexture produced by the coatings in this Example 19. As shown, threeparameters, a, b and c, are defined to describe certain planar featuresof the texture. These parameters are defined as follows: “a” representsthe distance between peaks of the texture, “b” represents the width ofeach textural feature, and “c” represents the length of each texturalfeature. These parameters were measured manually from the correspondingtraces and, therefore, may have substantial inherent error associatedwith them; however, they can be used to distinguish gross differencesbetween the textures. Regardless, these parameters should not be viewedor used as limiting the type, shape, or size of the macroscopic texture.The ranges for these parameters for the coatings produced in thisExample 19 are provided in Table 13. Gloss (60°) and gauge (thickness)measurements arm also given in Table 13 and follow the same conventionsas the gloss and gauge data presented in Example 18.

TABLE 13 Gloss and Texture Measurements for Air Knife Coated SamplesGloss Gauge Re- Ranges of Planar Sam- (60°) (mils) lief Dimensions(mils) ple In-line Trans. Min Max (mils) a b c 1 20.0 29.6 2.62 4.241.62  50-100 20-50 20-350 2 17.6 21.6 1.68 3.31 1.63 20-70 10-20 10-4003 23.3 30.5 0.66 1.06 0.40 10-20  5-10 20-100 4 62.4 58.0 0.97 1.44 0.475 37.4 36.0 0.45 0.85 0.40 6 74.9 75.3 2.62 2.62 0.00 7 16.9 17.1 0.611.61 1.00

These results show that it is possible to control the aggressiveness ofmacroscopic textures generated with an air knife by adjusting theprocess conditions. For the high viscosity coating that employs an RCAas part of its composition, the wave-like macroscopic textures progressfrom relatively large and broad features at fast line speeds to texturewith a very fine, satin finish at low line speeds. Note that even in thelatter case (FIGS. 28 and 31) the fine wave-like features can still bedistinguished with the unaided eye. Also note that the same pre-curedcoating composition was used in samples 1-3, illustrating theappreciable textural control that may be attained from the coatingapplication method alone.

Similar textural control is achieved using a coating withtexture-producing particles (“sandpaper” texture), as indicated by thelarge variations in gloss and relief shown in Table 13 for samples 4-7(similarly, a single pre-cured coating composition was used in samples4-7). In general, lower gloss and higher relief correspond to moreaggressive textures. However, variations in the planar dimensions and inthe average gauge (average of the minimum and maximum gauges) are alsoimportant for the overall perceived aggressiveness of the textures (andmay also influence gloss readings).

Example 20

This example shows the scratch resistance properties of cured coatinghaving macroscopic texture. The pre-cured coating mixtures 4 (40%nano-alumina) and 7 (22% nano-silica) in Example 6 and the coatingExample 12 (4% wax) were coated as described in Example 6 on flexiblevinyl sheet flooring and UV cured under inert conditions as described inExample 6. These cured coatings had macroscopic wave-like texture.Pieces measuring 9 in² were mounted on plywood and placed on the floorin a high traffic area (a cafeteria). After a given amount of time thefloor panels were pulled up, cleaned, and evaluated for scratchresistance. The scratch resistance was measured by counting the totalnumber of scratches on a given coating and dividing by the total area insquare feet. As controls, a standard high gloss (80-90%) macroscopicallysmooth urethane containing no inorganics and a wood laminate floor werealso evaluated. The results of these tests are shown in FIG. 33. Thescratch data clearly show that the textured urethane coatings have fewerscratches per square foot of exposed surface than the standard smoothurethane and the wood laminate.

Example 21

This example demonstrates a thermally-cured top coating that providesmacroscopic texture. The pre-cured coating composition described inTable 14 was mixed using a Cowles blade mixer at room temperature. Thiscomposition is nearly identical to the radiation-curable coating mixturedescribed in Examples 16 and 17 except that a thermally activatedinitiator (an organic peroxide) was used instead of a UV activatedinitiator to initiate the curing. This coating mixture was then appliedto flexible sheet vinyl at 70° C. using an air knife. The resultingcoated substrate (1-1.5 mils thick) was cured at 360° C. for 2 minutes.The resulting solid coating had a ceramic-like macro-texture, which asnearly identical in appearance to those coatings in Example 17.

TABLE 14 Thermally-Curable Coating Composition Coating ComponentManufacturer (Wt %) Urethane acrylate (Alua 1001) Congoleum 44.83Propoxylated diacrylate (SR 306) Sartomer 20.53 Ethoxylatedtrimethylolpropane triacrylate Sartomer 11.25 (SR 454) Ethoxylateddiacrylate (SR 259) Sartomer 6.92 Tertiary-butyl peroxybenzoate (P-20)Norac 1.06 60 μm Nylon 12 (Orgasol 2002 ES6) Atochem 6.25 5 μm Nylon 12(Orgaso 2001 UD) Atofina 8 35 nm Alumina (Nanotek alumina) Nanophase 1Prehydrolyzed silane (as described in Congoleum 0.16 Example 1)

Example 22

This example demonstrates the use of a shrinking wear layer to providetexture from the use of texture-producing particles. A wear layerformulation was made comprising, by weight, 57.8% PVC resin (75HCavailable from Oxychem, Dallas, Tex.), 6.4% PVC resin (567 availablefrom Oxychem, Dallas, Tex.), 26.6% plasticizer (N-6000 available fromVelsicol, Rosemont, Ill.), 2.9% plasticizer (S-375 available fromSolutia, St. Louis, Mo.), 1.9% plasticizer (A-150 available from Exxon,Houston, Tex.), and 4.4% stabilizer (2347 available from OMG, Cleveland,Ohio). To this mixture is added 25% solid glass beads (no plasticizerabsorption or melting) having a mean diameter of 203 μm (SpheriglassA-1922 available from Potters Industries, Valley Forge, Pa.). Theresulting wear layer mixture was coated with a draw bar at 10 mils on aflexible vinyl gel. The resulting sample was then fused at 385° F. for1.5 minutes. As a control, this same wear layer formulation without theglass beads was coated and gelled. The control plastisol had a visiblysmooth surface and a gloss value of 38%. The sample containing glassbeads had macroscopic texture and a gloss of 23%, which indicates thatthe wear layer decreased in thickness during gelation to expose theglass beads.

Example 23

To demonstrate wet flocking, a standard PVC plastisol (Ultima Wear LayerWB4 available from Congoleum Corporation, Mercerville, N.J.) was drawndown on flexible gelled PVC at 10 mils. Several types of particles, asdescribed in Table 15, were each wet flocked on the wet plastisol. Thesesamples were then fused at 385° F. for 1.5 minutes. The visualobservations as well as the gloss values for each sample are given inTable 16. The data in Table 16 indicate that wet flocking givesceramic-like texture as long as the plastisol is fused at a temperaturelower than the melting point of the particle. When the fusiontemperature is higher than the melting temperature of the particle, theparticle melts to form a semi-continuous film on the surface of theplastisol. This phenomenon occurred when Nylon 12 and polypropyleneparticles were used.

TABLE 15 Particles Used in Wet Flocking Diameter Melting pt TypeTradename Manuf. (μm) (° F.) Solid glass Sheriglass Potters 203 1300A1922 Industries Nylon 12 Oragsol 2002 Atofina 60 352 ES6 Nylon 66Ashley 70 513 Polymers Nylon 11 Ashley 100 388 Polymers polypropylenePropyltex 100 Micropowders 90 330 polypropylene Propyltex 140Micropowders 50 330

TABLE 16 Ultima Wear Layer Wet Flocked With Various Particles ParticleTexture Gloss (%) Comments None Smooth 50 Propyltex 100 Smooth 13Particles melted Propyltex 140 Smooth 12 Particles melted Nylon 12Smooth 11 Particles melted Nylon 11 Ceramic 3 Nylon 66 Ceramic 3.4 GlassCeramic 3

Example 24

This example illustrates the use of spray coating as a method forapplying a radiation-curable coating having macroscopic texture onto atile substrate. A pre-cured coating mixture having the compositiondescribed in Table 17 was applied to a vinyl tile substrate using anair-gun sprayer (Campbell Hausfeld Standard Duty Air-Driven Spray GunModel DH5300). The spray gun was operated in pressure-feed mode using 45psig of air pressure, and the nozzle configuration employed was designedfor external atomization of the coating droplets by the high-pressureair stream. The tile substrate was sprayed by multiple passes with thehandheld spray gun at a height of about 12″ from the tile surface untilcomplete coverage of the tile surface by the pre-cured coating mixturewas achieved. The sprayed-on, pre-cured coating mixture on the tilesubstrate was then cured as in Example 2. Both the sprayed-on, pre-curedcoating mixture on the tile substrate and the cured coating on the tilesubstrate exhibited macroscopic texture due to the texture-generatingparticles present in the pre-cured and cured topcoat.

TABLE 17 UV-Curable Coating Composition Component Wt. % UV-curable Resinfrom Table 1 84.59 Orgasol 2001 UD (5 micron organic flatting agent)8.00 Orgasol 2002 ES6 (60 micron texture-producing 6.25 particle)Nanotek Alumina (inorganic RCA) 1.00 Prehydrolyzed Z-6030 (couplingagent from 0.16 Example 1)

Example 25

This example shows the use of a roll-coat and air-station combinationprocess (termed a RAS process, as described previously) for applicationof a radiation-curable, macroscopically textured coating onto a tilesubstrate. Tile substrates were coated with the pre-cured coatingmixture described in Table 18 using a three-roll coater comprised of ahard rubber roll as the upper metering roll (about 90 Shore A Durometerhardness), an engraved steel roll (72 tri-helical) as the transfer roll,and a soft rubber roll as the applicator roll. An especially softdurometer (35 Shore A Durometer) for the applicator roll was chosen topromote coating application in deeply embossed grout lines and in otherdeeply embossed substrate regions. Line speed through the roll-coaterwas about 70 fpm (feet per minute), and the compression of theapplicator roll upon the tile substrate was about 115 mils. Theroll-coated tiles exhibited directional lines of texture due to“film-splitting” in the machine direction. Subsequent passage of theroll-coated tiles through an airstation removed this roll-coaterdirectionality. The air-station comprised a vacuum conveyor to hold downthe moving tiles, as well as an airknife operating at up to 3.7 psig atangles between +20° and −20° from vertical (vertical referring to theairknife slit pointing down directly upon the tile, and positive anglesreferring to the slit being angled toward the incoming tile). Theairstation line speed was 40 fpm with a knife-to-tile gap of 50 mils,and tiles were passed through with a planar rotation of 45° between theroll-coater directionality lines and the airstation machine direction.Moreover, two passes under the airknife were made, with 90° planarrotation of the tile between passes (i.e., on the second pass there is−45° planar tile rotation between the roll-coater directionality linesand the airstation machine direction). Finally, the pre-cured texturedcoating was subjected to a low-gloss cure cycle as follows: a) twoH-bulb (mercury) lamps on high at 125 fpm in air, then b) six H-bulb(mercury) lamps on high in nitrogen (˜3000 ppm residual O2) at 100 fpm.The final, UV-cured coating exhibits a low-gloss, macroscopicallytextured surface topcoat with textural features characteristic of the 60micron texture-generating particles present in the coating composition.

TABLE 18 UV-Curable Coating Composition Component Manufacturer Wt. %Ethoxylated trimethylolpropane triacrylate (SR Sartomer (Exton, PA)35.303 454) Polyester acrylate (Laromer PE56F) BASF (Charlotte, NC)41.050 Urethane acrylate (Alua 1001) Congoleum (Mercerville, NJ) 5.747Acylphosphine oxide (Luceirin TPO) BASF (Charlotte, NC) 0.330 AcematteOK 412 (3 micron inorganic flatting Degussa Corp. 8.000 agent)Prehydrolyzed Z-6030 (coupling agent from See Example 1 2.320 Example 1)Nanotek Alumina (inorganic RCA) Nanophase Technologies 1.000 (BurrRidge, IL) Orgasol 2002 ES6 (60 micron texture- Atofina 6.250 producingparticle) (Philadelphia, PA)

Example 26

The application of a radiation-curable coating having macroscopictexture onto a tile already pre-coated with a non-texturedradiation-curable coating is demonstrated in this example. Approximately5 g of a commercial, non-textured UV-curable urethane coating (AMT-475,available from Congoleum Corp., Mercerville, N.J.) was applied to a 12″square tile using a curtain coater. This undercoat was then partiallycured in an air environment using four H-bulb (mercury) lamps on highwith a line speed of 100 fpm (feet per minute). Next, a second and finaltopcoat containing macroscopic texture-producing particles and havingthe composition of Table 17 was applied with a roll-coater andair-station (RAS) process similar to that described in Example 25 (anexception being the use of a two-roll coater instead of the three-rollcoater described in Example 25). The double-coated tile was thensubjected to the following low gloss cure cycle for curing of the twotopcoat layers: a) two H-bulb (mercury) lamps on high at 100 fpm in air,then b) six H-bulb (mercury) lamps on high in nitrogen (˜3000 ppmresidual O2) at 100 fpm. The partial cure of the non-textured,UV-curable undercoat instills sufficient mechanical strength into theundercoat to withstand the subsequent roll-coating of the texturedtopcoat. At the same time, the partial undercoat cure also promotesadhesion of the textured topcoat to the undercoat via unreacted acrylatecrosslinking units that remain in the undercoat after partial cure andcan crosslink with similar reactive groups in the textured topcoat. Thefinal, UV-cured coating exhibits a low-gloss, macroscopically texturedsurface topcoat adhered to an underlying non-textured; UV-curedbasecoat.

While the foregoing description and drawings represent the preferredembodiments of the present invention, it will be understood that variousadditions, modifications and substitutions may be made therein withoutdeparting from the spirit and scope of the present invention as definedin the accompanying claims. In particular, it will be clear to thoseskilled in the art that the present invention may be embodied in otherspecific forms, structures, arrangements, proportions, and with otherelements, materials, and components, without departing from the spiritor essential characteristics thereof. The presently disclosedembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims, and not limited to the foregoingdescription.

1-56. (canceled)
 57. A coated flooring substrate, comprising: asubstrate having a top surface, and a cured resin coating having apredetermined thickness disposed on said top surface, wherein said curedresin coating comprises a plurality of particles, each having apredetermined size that is greater than said predetermined thickness ofsaid cured resin coating, and a visible texture provided by saidplurality of particles.